Many people find it very difficult to draw accurately in perspective. Even if they appreciate that lines in a drawing which notionally extend away from the viewer-what may be called lateral lines-must all aim at one or the other of two"vanishing points"on opposite sides of the drawing it is difficult to achieve this if the vanishing points have no visible presence.

The present invention facilitates drawing accurately in perspective by providing fixed "vanishing points"on opposite sides of a sheet of paper and guide means which will ensure that all lateral lines in a drawing are aimed at one or the other of them.

In accordance with the present invention there is provided a drawing aid comprising a support having a location for the sheet to be drawn upon the aid comprising means providing fixed points on the support on either side of the sheet intermediate the top and bottom of the sheet, guide means being provided which extends between and is deflectable angularly relative to said fixed points substantially throughout the height of the sheet such that straight lateral lines drawn with the aid of the guide means from opposite ends of an upright line on the sheet will have correct perspective, the fixed points acting as vanishing points.

Plural fixed points are preferably spaced along each side of the support each pair thereof having an equal spacing from the top or bottom of the support.

The support is preferably provided on opposite sides of a sheet location with plural holes spaced along each side of the support, each pair thereof having an equal spacing from the top or bottom of the support, and in that the fixed points are provided by a pair of pegs which can be inserted in selected holes on opposite sides of the sheet location.

The location for the sheet may be a rectangular recess within the support, the recess having parallel top and bottom and parallel side edges, and a ruler may be provided having parallel end edges locatable within the recess to be a sliding fit between the top and bottom edges or between the side edges of the recess.

The recess may be formed with grooves parallel with said edges thereof in which flanges projecting from the underside of the ruler may slide.

The guide means may comprise an elastic element which can be stretched between said fixed points, or a selected pair of said fixed points, the elastic element being threaded through a'rigid guide providing straight edges, the guide being shorter than the distance between said fixed points.

The fixed points are preferably provided by circular-section pegs engaging in bores in the support and the guide may have arcuate ends adapted to swing around the pegs.

Opposite ends of the elastic element may be connected to clips having formations which will engage respective recesses in opposite sides of the support. The pegs may depend from the undersides of the clips.

Alternatively or in addition guide means may be provided which comprises a pair of rigid, elongated guides articulated at one of their respective ends, each guide engaging a respective pivot means whereby each guide is movable angularly and longitudinally but not laterally relative to the associated pivot means.

Each rigid guide may engage the respective pivot means by means of a longitudinal slot.

Each pivot may comprise a pin upstanding from a clip, the clip having a formation whereby it may be engaged to a side of the support at a position where each said pin will provide one of said fixed points.

A preferred embodiment of the present invention will now be described by way of non- limitative example with reference to the accompanying drawings, in which: Figure 1 is a view from above of the frame or board of a drawing aid in accordance with the invention; Figure 2 illustrates a ruler for use with the board of Figure 1; Figure 3 is a view from above of a first guide assembly for use with the board of Figure 1; Figure 4 illustrates one end of the guide of Figure 3 inverted relative to Figure 3; Figure 5 is a view from above of a second guide assembly for use with the board of Figure 1, and Figure 6 is a view from below of one of the clips of the guide of Figure 5.

Referring first to Figure 1 a generally rectangular frame or board 10 has a recessed central region or well 12 in which a sheet of paper (not shown) will fit. The well 12 is dimensioned to accept a sheet of paper of a standard size, e. g. A4, A3 or foolscap. Near to the top and to the bottom of the well the board 10 is formed with parallel grooves 11 in which flanges 15 at opposite ends of a ruler 14 may engage. In use of the ruler 14 it can slide transversely of the board 10, the user positioning it where it is desired to draw a vertical line on the paper. Similar grooves 16 may be provided in the well 12 near to its lateral sides so that a second ruler (not shown) similar to the ruler 14 but appropriately longer can be used to draw horizontal lines.

Each lateral edge of the board 10 is formed with three undershot recesses 17, one pair lying on the horizontal centre line of the board 10 and the other two pairs being equally spaced respectively from the top and from the bottom edge of the well 12. In corresponding positions the lateral sides of the board 10 are formed each with three larger recesses or rebates 18 opening upwardly of board and inwardly of the well 12. Within each rebate 18 the board 10 is formed with a blind bore 19.

The guide means illustrated in Figures 3 and 4 comprises a length of elastic 20 extending between two similar clips 21. In its unstressed condition the elastic 20 is shorter than the horizontal width of the well 12 so that it has to be stretched to engage the clips 21 in a selected pair of the rebates 18. The elastic 20 is threaded through a tube 22, an upper side 23 of which is overshot to provide projections 24 and which provides parallel straight edges 25 and 26. Each projecting end 24 of the guide terminates in an arcuate formation 27.

Tabs 33 project upwardly from the upper surface of the guide and can be grasped to manipulate the guide.

The underside of each clip 21 has confronting L-shaped formations 28 and 29, inboard of which is a peg 30. Each end of the elastic 20 is tied to a bar 31 which engages behind the formation 29 of one of the clips 21, passing through a slot 32 in the latter.

In use of the guide of Figures 3 and 4 the clips 21 are engaged in a selected pair of the rebates 18. If the central pair is selected lines drawn using the guide will be as though the object being drawn is generally at eye level. If the upper pair is selected the drawing will be of an object below eye level, whereas if the lower pair is selected the drawing will be of an object above eye level. The L-shaped formations 28 of the clips 21 will fit into the recesses 17 while the pegs 30 will enter the blind bores 19. The L-shaped formations 29 ensure that the elastic 20 is not pinched between the clips and the board. With the elastic 20 stretched between the clips 21 the guide 22,23 can be moved along it until one of the arcuate ends 27 abuts one of the circular-section pegs 30, the end region 24 of the guide passing between the body of the clip 21 and the base of the recess 18. This enables the guide 23 to be smoothly pivoted about one or the other of the pegs 30. With the guide pivoting about the right-hand peg 30 the user will be able to draw lines converging to the right and with the guide pivoting about the left-hand peg the user will be able to draw lines converging to the left.

The alternative guide illustrated in Figures 5 and 6 comprises similar, rigid, longitudinally slotted arms 34 and 35 pivoted together at one of their respective ends by a pin (not shown)

which extends from a hub 36 having a radial formation 37 to assist in manipulating the device. Clips 21A associated with the guide of Figure 5 are similar to the clips 21 of the guide of Figures 3 and 4 except that they lack the formation 29 for engaging the elastic 20.

They have L-shaped formations 28A to engage a selected pair of the recesses 17 and pegs 30A to engage in the bores 19 of the associated rebates 18. Upstanding from the upper surface of each clip 21A is a pin 38 engaged in the slot 39 of the'associated arm 34 or 35.

Preferably and as shown each pin 38 has ahead 39 whereby each clip 21A is permanently engaged to the associated ann 34 or 35. This will prevent the clips 21A being mislaid.

In use of the guide of Figure 5 the formation 28A of each clip 21A is engaged in one of the recesses 17 of a selected pair, the peg 30A entering the associated bore 19. The guide can then be moved around e. g. by grasping the projection 37 so that one side of a selected arm 34 or 35 can be used to draw lines converging either to the left or to the right of the paper in the well 12.

In modifications of the invention which are not illustrated the well 12 may have shapes different from that illustrated. For example the board 10 may be square or vertically instead of horizontally elongated. Alternative ways to engage the elastic 20 to opposite sides of the well 12 or to provide pivots for the arms 34 and 35 may include simple pegs without clips 21 or 21A. The top surfaces of the top, bottom and side edges of the board 10 may be masked by a frame located over the board, and if this is used to hold the paper in place the well 12 may be dispensed with. Alternatively, or in addition, clips 40 may be provided at the comers of the well 12 to hold the paper clear of the grooves 11 and 16.

These grooves are not essential. The rule 14 need not have flanges 15 but may rely on straight top and bottom edges sliding along parallel top and bottom edges of the well 12 to maintain it vertical. The same applies to a possible horizontal rule.

The expressions vertical, horizontal, top, bottom, side, left and right are used herein and in the appended claims to mean these directions from the image being viewed on the paper in the well 12 when the board 10 is laid on a supporting surface such as a table or desk.

The components of the device illustrated may be made from a range of materials such as wood or metal but all can conveniently be manufactured from a plastics material.