This invention relates generally to methods of joining, in a removable way, secondary structural members to primary structures or structural members. It relates specifically to methods in which an anchor element is fixed to a primary structure or structural member, an adapter element is fixed to the anchor element and the adapter element able to accommodate and support the end of a secondary structural member; all able to be readily, partially or completely, dismantled for removal.

Situations are common in which it is necessary to connect a secondary structural member to a primary structure or structural member. Examples of such situations are: connection of bed side rails to bed heads or transverse members; connection of beams to uprights in shelving or pallet racking; assembly of scaffolding; assembly of pedestrian barriers; erection of exhibition booths; and assembly of other temporary structures. While it is also common for primary structures and structural members to be of a vertical orientation and secondary structural members to be of a horizontal orientation, many other orientations of both may be required.

In the Rail Fence and Bracket System taught by Bertato in CA 2 870 710, a fence system has upright posts and transverse fence rails, formed of hollow rectangular tubular construction and having internal ribs formed within the hollow interior; a plurality of angular- mounting brackets defining a transverse insertion portion and an upright attachment portion, and wherein the transverse insertion portions are adapted to make a frictional fit within the interior of said hollow tubular rails, and a plurality of fastening holes in said attachment portions, whereby the same may be secured to a fence post.

The Bracket Attachment System taught by Marron in US 2014/0231739 provides a universally adjustable metal two bracket attachment system for metal fence posts for the attachment of various types of fencing materials or fence sections; the subject metal fence post attachment bolt and bracket system being simple and easy to install, is universally adjustable to round or square metal fences posts, by bolting onto “off the shelf’ nonadj ustable fence post brackets; the subject brackets allowing both full section metal fencing with the bracket mounted with the open end side ways, and three rail metal fencing with the bracket facing up.

In the Attachment Mechanism and Fence System Using the Same taught by Rowley et al in US 2011/0001104, a fence system includes first and second posts attached in the ground and a rail coupled to the first post and the second post with a female member attachment mechanism and a lip; the fence system also including a slat including a male member attachment mechanism with a flap and a locking mechanism defining a step, the slat being coupled to the rail such that the male member attachment mechanism is coupled to the female member attachment mechanism and the step abuts the lip; should a force be applied to remove the male member attachment mechanism from the female member attachment mechanism, the lip exerts a force on the step resisting the force.

The Rail End Cover taught by McGinness et al in US 8,047,485 provides a universal rail mounting bracket for attachment of a handrail or fence rail to a support structure, a rail end cover being insertable over the rail end after the rail has been mounted to the support structure with the bracket, the rail end cover being provided to cover any unsightly gaps or uneven cuts which may have occurred during manufacture or installation of the rail.

The Clip for Adjustable Mounting of a Fence Rail to a Fence Post taught by Platt in US 2007/0045603 discloses a fence rail clip for attaching a fence rail to a vertical fence post, the rail clip having a bracket with a raised central area flanked by two lower lateral areas and a rail connector that, vertically or horizontally, slidingly engages the central area of the bracket, the lateral areas defining locations for connecting the bracket to a vertical post; the rail connector has a rail receiving receptacle into which an end of a rail may be inserted, the bracket optionally including indicia or characters for determining the correct position of attachment of the rail connector to the bracket; when the position of the rail connector is altered by sliding the rail connector relative to. the bracket, the angle of the rail receiving receptacle is altered, thereby changing the angle at which a rail may be attached to the post.

In the Stable, Non-locking Picket Fence System taught by Hellenbrand in US 2018/0320404, a fencing system has at least two engaging elements, two rails extending along respective upper and lower rail axes with a generally hollow rectangular or four-sided cross-section; the rails have a horizontal top wall between first and second vertical rail sidewalls that depend downwardly to define an internal cavity, at least two attachment legs extend inwardly towards each other from the sidewalls, vertical picket posts extend between through holes in the upper and lower horizontal rails; the picket post includes multiple grooves, the grooves receiving the posts without penetration into any internal cavities of the upper and lower rail, and the posts are forced inwardly into the grooves by elastic memory in the sidewalls, the posts within grooves not being in locked engagement with the grooves, but held in place by the force of the elastic memory, the posts withdrawable from the grooves by overcoming the elastic force.

The Fencing System taught by Moreby et al in GB 2 094 368 comprises two posts and a cross rail, the posts each having a first attachment means which interengage with a second attachment means of the cross rail upon movement of the cross rail in a predetermined path transverse to the longitudinal axis thereof releasably to attach the cross rail to the posts so that the cross rail extends between and is supported by the posts; a fencing panel and means releasably to connect the fencing panel to the cross rail, the means hooking into a staple, the connecting means being a resilient clip which hooks behind a rail on the fencing panel and clips over the cross rail, the bottom of the posts being wedgeable to a base plate.

The Fastening Clip for Attaching Rails and Posts in Fence Structure and Attachment Method of the Same taught by Ratanasiriwilai in US 2007/0034846 comprises a post clipping portion for clipping an outer surface of the post wherein each end region thereof is a connecting portion, and each end of the connecting portions is a rail clipping portion having an upper end or a lower end being a rail-edge clipping portion for clipping an upper surface or a lower surface of the rail respectively and the rail clipping portion has a through hole for inserting of a bolt.

The Temporary Protective Handrail Connecting Device for Stairs taught by Yang et al in CN215889434 comprises a fixing plate and a fixing steel pipe, and a connecting adjusting mechanism arranged outside the fixing steel pipe, the connecting adjusting mechanism comprising a plurality of mounting blocks mounted outside the fixed steel pipe with every two adjacent mounting blocks being perpendicular to each other, adjusting grooves being formed in the mounting blocks, balls are rotationally connected into the adjusting grooves, connecting columns are mounted outside the balls, and ring sleeves are mounted at the ends, away from the balls of the connecting columns; the interior of the ring sleeve is slidably connected with a protection steel pipe, and the interior of the ring sleeve and the interior of the protection steel pipe arc jointly slidably connected with an antidisengaging rod, the installation angle of the protective barrier being adjustable through the cooperative use of the installation block, the adjusting groove, the ball body and the ring sleeve; the arrangement resulting in a great improvement of the safety of the protective bander, during installation of the protective barrier the uncomfortable angle of the ring sleeve is avoided, and the butt joint of the protective barrier at various angles is facilitated.

In the Bracket for Fence Rail or Panel taught by Perry in GB 2 401 616 a fence bracket comprises a main body which may be rectangular, square, semicircular or triangular in correspondence to the cross-section of a fence rail, and has at least two flanges adapted to overlie a side of the rail or panel, and at least one tab with at least one hole for securing the bracket to the face of a fence post, the bracket being attachable to the panel or rail before attachment to the fence post, the flanges and tabs optionally being rectangular, triangular, or part-circular.

The Rail and Fence Bracket Apparatus taught by Spruill in US 6,543,751 includes a back piece, a bottom piece, and a bottom support system, the back piece including screw attachment openings, the edges of the bracket being adapted to facilitate installation of a supported rail, an offset spacer being attached to the back piece to allow for air circulation around said supported piece, the bottom piece able to be curved to support rounded rails and include a water passage opening to allow for drainage, the bottom support system including an angle bracket, the bracket joints being strengthened with fillets, side pieces being provided for supporting and holding the installed rail; the unit is able to be designed with an engineered failure mode to allow for bracket failure to occur before a rail failure would occur, a rail retaining system may be used to retain the rail in position and a rail slot extension may be used to support the bracket in association with a rail cutout.

The Fence Construction System taught be Espinueva in US 5,192,056 allows for simple and rapid construction of a wooden fence, the system including upper and lower metal brackets for fastening horizontal rail members to vertical fence posts; included in the system are quick attachment means for rapid assembly of the fence, the system allowing a durable traditional style good neighbor fence to be rapidly assembled from precut or standard sized lumber.

In the Multi-component Conical Comer Structure for Shelving taught by McAllister et al in US 2010/0108631 a shelving unit comprises a plurality of upright support posts and shelves having multiple comers with a multi-component corner structure at each comer of the shelf for releasably connecting the shelf to the posts, each corner structure comprising a two piece base segment and a substantially frictionless outside interlocking segment, the two piece base segment including a housing fixedly connected to a shelf comer and a substantially frictionless inner liner within the housing, the outside interconnecting segment including outwardly extending flanges that engage vertically oriented opposed undercut slots on the inner liner to facilitate interconnection of the base and interlocking segments; both segments include partial frusto conical surface portions that engage a frusto conical clamping sleeve on the support posts to facilitate releasable connection of the shelf to the posts, the substantially frictionless material of the inner liner and outside interlocking segment enabling ease of assembly and disassembly as well as a tight wedging fit of the components.

In the Mechanical Fastener for Frame of Bed taught by Fouks et al in US 3,780,386, great flexibility of use and reduction of inventory are made possible by the convertible bed rail connector means which allows connection of a bed rail means to a bed post means alternately by hook means or bolted means while at the same time allowing the bed rail means to either support the bed post means as would be the case in a “Hollywood” bed arrangement or will allow the bed rail means to be supported by the bed post means as is the case in a conventional bed stead arrangement; an angular bracket member is movably coupled to a bed rail means so that hook means on the bed rail means may pass through a slot in the bracket to effect hook coupling means and to be retracted to a position where the bracket may be connected to the bed post means for either supporting the bed rail means or being supported by the bed rail means.

In the Bed Frame Having Releasably Interlocked Side Rails and Crossbars taught by Spitz in US 3,952,345 a bed frame of the knockdown type has a pair of side rails and at least one connected adjustable end crossbar cooperable to provide a supporting frame structure for an associated box spring, in which brackets on the side rails are formed to provide sockets for respectively laterally receiving associated end portions of a crossbar* therein into seated position where coacting parts respectively on the brackets and crossbar have interlocking engagement and function to retain the end portion of the crossbar against endwise withdrawal from the associated socket.

The Temporary Protective Barrier With Adjustable Angle taught by Shen et al in CN214996247 comprises vertical rods and transverse rods, the transverse rods being connected between the adjacent vertical rods through connecting shafts, the vertical rod comprising a connecting plate and a rod body, the connecting plate being arranged at the bottom end of the rod body with connecting holes formed in the rod body at intervals, the cross rods being movably connected into the connecting holes; the cross rod is movably connected in the vertical rod, the angle of the cross rod being adjustable up and down so that the ladder stand is suitable for base structures such as stairs and ramps with different inclined planes and angles; turnover utilization rate and applicability are high and the ladder stand does not need to be produced in batches independently according to the existing structure; the device has the advantages of simple structure, light weight and convenience in assembly and disassembly, saves a large amount of manual assembly and disassembly time and cost, improves the construction efficiency, and effectively reduces the cost.

In the Dovetail Joint Construction taught by Lutz in US 5,762,410, one or a pair of aligned dovetail grooves secure various shelves to supports depending upon whether the shelf is an upper or lower unit, vertical supports have male dovetail projections formed on each end for mating with a groove, a wedge projection is formed on the support end adjacent to the male dovetail projection for wedging against the shelf in interference fit when the male and female elements are assembled, the supports have a width less than that of the shelves so that the dovetail joints are only visible from the shelving rear, the wedge projections are sufficiently small so as to not be observable from the shelving front; a particular- shelf construction employs upper and lower shelves each comprising a dual construction of an upper and lower member, a triangular brace is secured to the lowermost shelf for support when the shelving is hung on a wall; all shelving members and supports are secured by identical dovetail joints and are collapsible since no dowels or adhesive is used to permanently secure the elements.

In the Shelving Beam taught by Lynch in NZ 512360, a demountable shelving beam is provided for use between opposing sides of two spaced apart shelving uprights, two sets of end lugs with rebates inward thereof being provided, one above the other at each end of the beam, at one end of the beam the rebates being of elongate form running longitudinally of the beam, at the other end the rebates being in the form of an inverted “V” shape adjacent the lugs with a ramp leading downwardly and away from the rebates; the spacing of the lugs above one another match the spacing of slots in the sides of the uprights; assembly being by first presenting the end of the beam to the upright and inserting the lugs into the slots such that the side wall of the upright locates in the rebates, moving the beam to provide clearance for its end to be presented to the opposing side of the upright, the beam then being moved to insert the lugs at that end into the associated slots thereof; by downwardly pressing the beam end the engagement of the ramp of the wall of the upright dislodges the beam wedging the wall of the upright in the inverted “V” shaped rebates, the action also causing the lugs at end of the beam to butt up on the inside of the wall upright, thus interlocking the beam in place; the beam is demounted using the reverse procedure.

In the Improvements Relating to Shelving Structures taught by Barratt in GB 2 354 934, a shelving structure includes receiving members and shelf support members, the receiving members being provided with ‘P’ shaped, keyhole apertures, the shelf mounting members being provided with primarily U shaped connectors comprising an engagement part and a retention part; in operation connectors are inserted into the apertures and moved downwards causing the retention parts to lie flat against the receiving members, thus preventing lateral movement between the members; a slight tapering of the narrow part of the apertures serves to retain the engagement of the connectors in a wedging fit.

In the Improvements in Shelving Systems taught by Maxwell in GB 1311960, a shelf support comprises a wall mountable upright with a planar front surface and longitudinal grooves in its side edges, a shelf bracket and a pair of clamps with flanges which engage the grooves and the bracket so that a part of the bracket is clamped to the upright between its front surface and a part of the clamps; the clamps being drawn together by a screw to cause wedging engagement of similarly inclined faces of the upright and the clamps whereby the bracket is forced into engagement with the front surface.

In the Scaffolding System taught by Peralta in DE19919358, vertical tube uprights and individual and/or multiple railing tubes comprise a scaffolding with holding devices for fixture of one of the railing tubes to the tube uprights, wedge boxes being provided on the uprights for fixture in relation to an opposing wall at an angle to them, locking components being provided for wedging the railing tubes, which have at least one guide slot engaged with the wedge box, each locking component having a spring component for wedging the railing tube in its locked position.

In the Improvements in Fencing taught by Moore in GB 599,042, a fence is built up of uprights connected by horizontal rails, the enclosed space being filled by a network consisting of horizontal and vertical elements welded together at their intersections, the uprights a being of T or of channel section, and the rails of L-section, the vertical elements of the net passing through holes in the horizontal parts of the rails, the attachment of the rails to the posts being effected by providing a slot in each end of the rails and a column of similar slots at top and bottom of the posts, a deformable staple being passed through a selected pair of slots and the slots in the two abutting rails, the slots allowing the rails to be suitably adjusted above the ground, and permitting the fence to be erected up and down a slope; the lower end of each post may be pointed and passed through a slot in an Lpiece buried in the ground, or the end may be simply buried in concrete blocks, intermediate round rods may pass through both rails and be welded thereto and to the net; a gate is formed by bending an angle strip into D form and fitting a vertical across its ends, network being inserted as before; a modified form of fence is provided having a tubular top rail and tubular uprights, the connection being effected by a cap having flanges and depending tongues joined together by a bridge and plugged into the uprights, lugs depending from the cap engaging the rails and the tops of the uprights are suitably recessed to receive the rails, half-straps are riveted to, and embrace, the lower ends of the uprights for bolt and nut attachment to the angular bottom rails.

In the Fence and Fence Connection Apparatus and Method taught by Goedecke in WO 2017/100040 a connector assembly and method are provided for the construction of a no-weld pipe fence, a no- weld fence end brace, or a no-weld fence comer brace, the connector assembly including (a) a bolt, a threaded pin, or a hinge knuckle structure which is attachable to a fence post and (b) an attachment sleeve which can be slidably nested on the end of a pipe rail or brace member, the attachment sleeve being connectable to the bolt, threaded pin, or hinge knuckle structure in a manner which allows the pipe rail or brace member to be pivoted to a horizontal position or to any other desired angle on the fence post and then locked in place.

In the prior art examples detailed, some are complicated, requiring multiple manufacturing processes for their production, rendering them unnecessarily expensive; some require specific tools to install or dismantle them and are not adapted for ready removal; some have an untidy and unattractive ‘mechanical’ appearance; some are limited to the use of specific materials; and some are made for narrow or specific applications.

The object of the present invention is to provide a connection system employing a small number of designs with applicability to multiple applications; a system adapted to high volume production, using high-rate, repetition manufacturing processes at a low production cost; a system that is able to be installed and dismantled quickly and easily with a minimum of tools; a system the components of which are easily coloured during the manufacturing process; a system having components of a neat, attractive appearance; a system the components of which may be made from metal alloy or polymer materials; and a system readily adapted to a variety of applications.

According to the present invention, a connection system adaptable to a variety of applications comprises an anchor element fixed to a primary structure or structural member, an adaptor element slidingly engaged with and lockable to the anchor element, and a secondary structural member engaged with and secured to the adaptor element, the adaptor element being made in a range of forms to accommodate secondary structural members of a variety of transverse cross-sectional shapes. Various provisions are made to fix the anchor element to different surfaces for different applications and an embodiment is provided in which the adaptor element is pivotally supported to permit the angular displacement of the secondary structural member.

The various aspects of the present invention will be more readily understood by reference to the following description of preferred embodiments given in relation to the accompanying drawings in which:

Figure 1 is a composite isometric view of the anchor element, adaptor element and structural member of the present invention;

Figure 2 is a face view of the interior of the adaptor element;

Figure 3 is a face view of the outer surface of the anchor element;

Figure 4 is a side view of the anchor element of Figure 3;

Figure 5 is a transverse cross-sectional view on A-A of the anchor element of Figure 3;

Figure 6 is a fragmentary view of one corner of the adaptor element of Figure 2;

Figure 7 is a face view of the outer surface of the anchor element of Figure 3 adapted for the installation of locking provisions;

Figure 8 is a face view of the interior of the adaptor element of Figure 2 adapted for the installation of locking provisions;

Figure 9 is a longitudinal cross-sectional view through a medial plane parallel to the greater sides of the adaptor element of Figure 2 said adaptor element having been adapted for the installation of locking provisions;

Figure 10 is a superior view of the adaptor element of Figure 2 showing the use of a security screw to operate locking provisions;

Figure 11 is a superior view of the adaptor element of Figure 2 showing the use of a key to operate locking provisions;

Figure 12 is a vertical cross-sectional view through a medial plane of a first method of fixing the anchor element to a surface;

Figure 13 is a fragmentary face view of a second method of fixing the anchor element to a surface;

Figure 14 is a fragmentary face view of a third method of fixing the anchor element to a surface;

Figure 15 is a fragmentary vertical cross-sectional view through a medial plane of the method of fixing of figure 14;

Figure 16 is a side view of an alternative embodiment in which the adaptor element is pivotally supported to permit the angular displacement of the structural member.

With reference to Figure 1, a connection system adaptable to a variety of applications comprises an anchor element 1 able to be fixed to a primary structure or structural member in a variety of ways, an adaptor element 2 slidingly engaged with the parallel, angled side edges of said anchor element and lockable to said anchor element, and a secondary structural member 3 engaged with and secured to said adaptor element, said adaptor element being made in a range of forms to accommodate secondary structural members of a variety of transverse cross-sectional shapes. While it is common for primary structures and structural members to be of a vertical orientation and secondary structural members to be of a horizontal orientation, other orientations of both may be required, the present invention being adaptable to accommodate these.

Said anchor element takes the form of a rectangular block having a ratio of thickness to overall width falling in the range 1:7.5 to 1:15.

With additional reference to Figures 3 to 5, said anchor element has formed on its upper central edge a toe 5 which engages a complementary recess 20 in the upper edge of said adapter element (as depicted in Figure 9), engagement of said toe with said recess acting as an indicator of the full seating of said adaptor element on said anchor element. A plurality of bores 4 pass through the thickness of said anchor element, two or more of^aid bores accommodating suitable fastenings employed to fix said anchor element to a surface. In the preferred embodiment, where said surfaces are of a polymer material or light-gauge metal alloy material, said fastenings take the form of self-drilling and self-tapping screws of the type commonly known as Tek Screws. Said boxes are provided at their enter ends with suitable recesses 14 of a diameter and depth to fully accommodate the heads of said fastenings. Said anchor element is optionally provided with a generally centrally4ocated bore of suitable diameter passing through its thickness, the axis of said bore being collinear with the axis of a complementary bore 21 passing through body 62 of said adaptor element such that, when said adaptor dement is felly seated on said anchor element, a single fastener passing through both said bores being optionally employed to lock, said ad^jfor element to said anchor element Said anchor element is optionally provided with an elongated recess 6 of square, rectangular or round cross-sectiosial shape located approximately medially in one side and extending inwardly (transversely) from one side for up to 50 per cent of die width of said anchor element, said recess coinciding with a complementary aperture 7 formed in the appropriate side of said adaptor element when said adaptor element is felly seated on saidanchor element A rod 8 of a suitable rigid material, is inserted through said aperture and fully into said recess to look said adaptor element to said anchor element, said rod being retained in place by frictional effects. Said anchor element having been fixed to a surface with its inner surface 23 abuting, said adaptor element is fixed to It by sliding down over said anchor element a longitudinally-ananged channel (depicted as 21 In Figure 9) formed in the flat, inner surface of said adaptor element and having a width and depth complementary to those of said anchor element, said sliding engagement being continued until said toe is fully engaged with, sold complementary recess. Sides 22 of said anchor element are angled in the manner of the dovetail slideway of a machine tool, making said anchor element widest at its outer surface, the sides of said longitudinal channel being angled similarly, said angled surfaces acting to retain said adaptor element on said anchor element, the widths of said longitudinal channel and said anchor element being such as to just permit said sliding engagement.

Said adaptor element having been fixed to said anchor element, the end of a secondary structural member 3 is inserted into said adaptor element, the thickness of the walls of said secondary structural member being accommodated in peripheral xone 11 between the outer surfaces of outwardly-projecting, rigid fingers 9 positioned Immediately adjacent and inwardly of the corners of the open end of said adaptor element and a plurality of narnw ribs 10 formed on the inner surface of skirt 24 formed around the periphery of said adaptor element, said ribs being arranged parallel to tire longitudinal axis of said secondary structural member. Said fingers, located immediately inwards of the comers of the open end of said adapter element, act to guide said secondary structural member into said peripheral zone, elastically deflecting as required to accommodate the end thickness of sold secondary structural member, said ribs acting to increase the frietional engagement of said secondary structural member with said adaptor element. Webs 12, 13 fixed to body 62 of said adapter element join said fingers and thereby provide bracing. Where more positive atachment of said secondary structural member to said adaptor element, is required, said structural member is optionally bonded Into place. Where a tensile force is to be applied to said structural member, suitable fastenings are employed io fix said structural member to said adaptor element.

With additional reference to Figure 6, where said secondary structwal member forms the top or bottom rail of a fence, gate or like structure it may be necessary to have another secondary structural member neatly abutting its upper or lower surface. As the adjacent said skirt of said adaptor element may prevent such abutment, provision is made to break out a panel from the appropriate lower or upper said skirt of said adaptor element, said panels being rendered readily removable by the provision of suitably located weakening grooves 19 formed in the inner surface of said skirt. Said panels are broken out simply by gripping them with a suitable implement and applying a modest force. Similarly, as the lower edge part of said anchor element may prevent such abutment, provision is made to break away said lower edge part, said lower edge part being rendered readily removable by the provision of a suitably located weakening groove 17 formed in the outer surface of said anchor element, a centrally-located recess 16 being provided tor the insertion of a suitable implement to effect said breaking away.

With reference to Figures 7, 8 and 11, in an alternative embodiment, said adaptor element is releasably locked to said anchor element by means of a key (not show) inserted in a keyhole to operate a tumbler mechanism (not shown) accommodated within boss 26 formed on the interior of said adaptor element. Rotational displacement of said key and said tumbler mechanism in the correct sense causes rotation of shaft 27, thereby displacing tongue inwardly through aperture 29 provided in the inner wall of said adaptor element, allowing said tongue to engage complementary slot 30 provided in the outer surface of said anchor element. Location of said tongue in said slot of said anchor element and removal of said key acts to securely fix said adaptor element to said anchor element. If necessary, the end of said secondary structural member is cut away locally to accommodate said boss. With reference to Figure 10, the lock mechanism described in relation to Figure 8 is deleted and said shaft is simply turned by a tamper-proof screw of one of the types well known in the art. Such screw types include the Two Hole Screw (depicted as 35 in Figure 10), 6-Lobe Star Drive Screw, Pin Hex Screw or Tri Slot Screw. The heads of said screws are recessed into said adaptor element to prevent their being gripped by pliers or similar tools, said adaptor element having been locked to said anchor element in the said way, can only be released using the appropriate tool. The locking in place of said adaptor element and, therefore, said secondary structural member is useful in situations where some secure form of temporary bander or structure is required to be maintained for some time.

With reference to Figure 9, in another alternative embodiment, said adaptor element is releasably locked to said anchor element by means of a plunger 30 passing through aperture 33 provided in the inner wall of said adaptor element to enter a complementary recess (not shown) formed in the outer surface of said anchor element. Said plunger is formed on arm 31 pivotally supported on pivot 32, spring means (not shown) being provided to urge said plunger into said recess. Said arm is extended to create concealed trigger 34 extending downwardly, access to said trigger being obtained through a suitable slot provided in the lower surface of said secondary structural member. The latching in place of said adaptor element and, therefore, said structural member is useful in situations where some form of barrier or structure is required to be temporarily maintained.

With reference to Figure 12, in another alternative embodiment, anchor element 1 is fixed to metal plate surface 36 by means of a single bolt and nut 37, 38 passing through more or less centrally-located bore 39 in said anchor element. One or more short pins 40 protruding inwardly from said anchor element enter complementary bores in said metal plate and act to positionally locate said anchor element. Said embodiment provides ease of attachment and removal of said anchor element. Obviously, one or more single light fastenings passing through said anchor element and tapped into said metal plate may be used to stabilise the position of said anchor element in place of said pins, but with reduced ease of attachment and removal.

With reference to Figure 13, in another alternative embodiment, anchor element 1 is fixed to surface 42 by means of two or more short pins 43 with enlarged heads (depicted in broken line as 44) passing through keyhole-type apertures in said surface. Said enlarged heads are passed through the larger openings 45 of said keyhole apertures, said anchor element then being linearly displaced to enter said pins into the narrow parts of said keyhole apertures, the lengths of said pins being such as to just provide a working clearance between said surface and the undersides of said enlarged heads. Accommodated within square or reciangnlar aperture 47 provided hi said surface is blocking piece 49 rotationally supported front said anchor element on shaft 48, said shaft being rotatable in said anchor element using a simple tool. In the position of said anchor element in which said enlarged heads are presented to said larger openings, said blocking piece is positioned parallel to and adjacent the tipper edge of said aperture. As said anchor element is displaced to enter said phis into said narrow parts of said keyhole apertures, said blocking piece is simultaneously displaced to a position in which it is parallel to and adjacent the lower edge of said apert ure. Rotation of said shaft through 90 degrees in the appropriate sense then brings the fee end of said

, blocking piece Into contact with the upper edge of said aperture, thereby preventing displacement of said anchor element to release said headed pins. .In the preferred embodiment, detents are provided to positively retain said blocking piece in its un-displaced , and displaced positions. Said embodiment provides ease of atachment and removal of said.. anchor element Obviously, one or more single light fastenings passing through said anchor .,. element and tapped into said surface may be used to lock said anchor element in place on said surface, but with reduced ease of attachment and removal. With reference to Figures 14 and 15, anchor element I is fixed to surface 50 by means of two or more two or more short pins 51 with enlarged heads 53 fixed in bores 52 in said anchor element engaging keyhole-type apertures in said surface. Said keybole-type apertures comprise larger openings 55 extending from which are arcuate narrow parts 56. In fixing said anchor element to said surface, said enlarged heads are passed through said larger openings of said keyhole apertures, said anchor element then being rotationally displaced to enter said pins Into the narrow parts of said keyhole apertures, the lengths of said pins being such as to just provide a working clearance between said surface and the undersides of said enlarged beads. In the preferred embodiment, the edges of said heads are turned down slightly to provide a frictional engagement with said surface. Rotation of said anchor element brings it Into a position in which said adaptor element can be fixed to it, said adaptor element thus being positioned to receive said secondary siruciural member, engagement of said structural member with said adaptor element preventing rotation of said anchor element to release said pins from said keyhole-type apertures. Said embodiment provides ease of attachment and removal of said anchor element.

With reference to Figure 16, an alternative embodiment, adaptor element 2 is fixed to said anchor element (not shown) in the manner described in relation to Figures 3 to 5, said channel with angled sides being formed in adaptor element base 57. Formed on said base are two outwardly-projecting, vertically-orientated, parallel supporting plates 58, adaptor collar 59 being pivotally supported on said supporting plates on pivot shaft 60. Secondary structural member 3 is inserted into said adaptor collar, said adaptor collar having the rigid fingers and plurality of narrow ribs formed on the inner surface of the skirt of said adaptor collar, said features being generally as described in relation to Figure 2. In the preferred embodiment, said supporting plates are made part-circular and of a diameter and spacing such that they may be accommodated within said adaptor collar, said adaptor collar being enlarged as required to provide accommodation for said supporting plates. The angular freedom of movement of said adaptor collar is determined by the length and shaping of said supporting plates and the adaptation of said adaptor collar, such as the cutting away of inner edges 61.

In alternative embodiments (not shown), said adaptor element is made with a cavity shaped to receive secondary structural members of a variety of transverse cross-sectional shapes. Such cross-sectional shapes include, square, rectangular, round, oval, D-shaped, hexagonal, octagonal, ribbed, grooved or other specialised form.

The fact that mating components of the present invention are drawn to different scales is of no significance.

The present invention should be taken to include any feasible combination of features described herein.