In new buildings, instead of plastering the interior walls, it is more efficient and cost effective to fix wall boards to the walls. The term"wall board"is used herein to include a board of any composition used to cover a wall.

The most commonly used form of wall board is plaster board (also known as sheet rock), but the term is also intended to include other wall coverings such as cement board and fibre board.

Interior walls are often constructed by securing wall boards to a stud work frame assembled from wooden or sometimes aluminium studs. They can also be constructed by securing wall boards to walls made of bricks or other building blocks with the aid of a dry wall adhesive.

Electrical wiring and plumbing are carried out before the wall boards are secured in place, as this obviously simplifies the work of the electricians and plumbers.

Because of this, at the time of mounting the wall boards, it is necessary to make holes in the wall boards to align with the open outlet boxes that are mounted by the electricians to receive electrical sockets and light switches.

Similarly, holes may be required to fit the board around plumbing equipment, such as shower taps and controls.

Hitherto, such holes have had to be made by measuring and cutting out the holes before offering the wall board to the wall. This is time wasting and can also be quite inaccurate, leaving larger gaps around electrical boxes than would conform with modern building regulations.

US 4,059, 905 discloses an apparatus for locating access openings for electrical outlet boxes. A locating assembly carrying one or more locator pins is positioned on the outlet box. The locator pins pierce the wall covering and allow a template to be positioned on the wall covering to make the desired cut out to fit over the outlet box. A similar device is disclosed in US 6,055, 736 which differs only in the manner in which the assembly carrying the locating pins is positioned on the outlet box.

In both of the above prior art patents, the pins used are circular cross section and small diameter. Because of the circular cross section, when only one pin is used, it cannot ensure the correct orientation of the cutting template relative to the locating assembly. When two or more pins are used, the locating assembly tends to become firmly anchored to the wall board on first contact. When fine adjustment is made to the position of the wall board, to align it with the ceiling or an adjacent wall board, the locating assembly moves relative to the outlet box instead of remaining correctly aligned with the outlet box and moving relative to the wall board.

With a view to mitigating the foregoing disadvantages the present invention provides an alignment tool for use in making a hole in a wall board to align with a pre-mounted box, comprising a locating assembly having a base for mounting in a predetermined position in the pre-mounted box, a template for cutting a hole of the correct size and shape in the board to fit around the box, and alignment means for passing through the wall board to align the template with the locating assembly, characterised in that the alignment means comprises a single post of non-circular cross-section projecting from the base of the locating assembly to pass through the wall board, and an aperture of complementary cross-section in the template for snugly receiving a portion of the post protruding from the wall board so as to ensure

the correct position and orientation of the template relative to the box.

Preferably, the post has a pointed end for piercing through the wall board.

The base of the locating assembly is conveniently formed of a flat plate to fit over the mouth of the box and a set of feet with tapering sides may project from the rear of the plate to engage the sides of the box in order to position the locating assembly relative to the box.

Advantageously, the feet are formed of a rubber-like material to provide frictional engagement between the feet and the sides of the box.

It is further preferred for the post to be formed of sheet metal.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which : Figure 1 is a perspective view of the locating assembly and the template of an alignment tool of the present invention, Figure 2 shows a vertical section through a wall showing the alignment tool of Figure 1 in use, Figure 3 is a side view of an alignment tool of a second embodiment of the invention, and Figure 4 is transverse section through the locating assembly of the alignment tool shown in Figure 3.

The alignment tool shown in Figures 1 and 2 comprises a locating assembly and a template, which are generally designated 10 and 12, respectively. The locating assembly 10 comprises a square base plate 14 fitted with four tapered rubber feet 16. A post 18 of square cross section having a

pointed end 20 projects from the plate 14 and is non- rotatably secured to it by means of a screw 22, shown in Figure 2. The template 12 is formed of a square plate 22 having a square hole 24 for receiving the square post 18 of the locating assembly 10 with minimal clearance.

The alignment tool is intended to assist in cutting a hole in a wall board to fit around a pre-mounted box, such as an outlet box for receiving an electrical power point or a light switch.

Figure 2 shows a box 30 pre-mounted on a stud 36 to which a wall board 32 is to be secured. Prior to offering the wall board to the stud work, the locating assembly 10 art is positioned over the mouth of the box 30. The tapered rubber feet 16 grip the side walls of the box 30 and hold the first part temporarily in place.

Though tapering rubber feet are advantageous on account of their simplicity, both in manufacture and easy of use, it would be possible to resort various alternative means of holding the locating assembly 10 in place against the box 30. It would, for example, be possible to use spring clips or to screw the plate 14 to the box 30 using the standard threaded connectors 38 provided in the box 30 for mounting of electrical sockets and light switches but this would clearly be more time consuming. It is also possible by suitably dimensioning the plate 14 to rely on the natural resilience of the sides of the box 30 to hold the locating assembly in place After the locating assembly 10 has been fitted over the mouth of the box 30, the wall board is pushed against the stud work, in the process impaling the wall board 32 on the pointed square post 18. Plaster board will be deformed around the post 18 but this is not of any consequence as the damaged section of the wall board will subsequently be cut

away. Indeed, it is desirable for the wall board to break around the post so that if the wall board is later moved the post will move in the pierced hole.

The plate 22 is now slid over the projecting end of the post 18. The plate 22 is designed to act as a template for a hole of just the correct shape and size to fit around the box 30. Because the post 18 and the hole 24 are square, the correct orientation of the template is guaranteed.

A knife 34 is then used to cut into the wall board 32 following the outline of the plate 22. After the board has been cut around the entire periphery of the box 30, by pulling on the post 18 it is possible to extract the locating assembly 10 through the hole that has been cut in the wall board 32 leaving a square hole that is in correct alignment with the box 30.

The embodiment of Figures 3 and 4 differs significantly from that of Figures 1 and 2 only in so far as concerns the construction of the post and its method of retention on the base plate of the locating assembly. To avoid unnecessary repetition, parts performing the analogous function to that previously described have been allocated reference numerals modified by the addition of 100.

In the embodiment of Figures 3 and 4, the post 118 is made of sheet metal. At its lower end, the sides of the post are cut away to define a tongue 140. The tongue passes through a hole of the same size in the 114 of the locating assembly 110 so that the shoulders defining the tongue 140 come to rest on the base plate 114. A rolled steel pin 142 is inserted into a transverse hole in the tongue 140 to prevent the post 118 from being pulled out of the base plate 110 and because of the spring tension in the rolled steel pin 142, it firmly pushes the base plate 114 against the

shoulders of the post 118 to maintain the post 118 perpendicular to the base plate 114.

The embodiment of Figures 3 and 4 is less costly to manufacture and assemble and avoids any possibility of the post rotating relative to the base plate. It will also be noted that the rubber feet have been omitted, further assisting in reducing manufacturing cost.

It will be clear that various modifications may be made to the described embodiment of the invention without departing from the scope of the invention as set forth in the appended claims. For example, the plate 22 of the template need not be square nor need it be of the same shape as the base plate 14 of the locating assembly. It can be of any shape and size to fit within and be retained by the pre- mounted box 30.

It is also not essential for the post 18 to have a pointed end as a rough hole can be pre-cut in the wall board to line up with the post.