Getting to the right point

Those who torture themselves with DIY will know that screwing a shelf to the wall is only part of the problem. First, you have to make the holes in the right place.

A common technique is to place the item against the wall or floor and - provided the screw hole is wide enough - insert a pen to mark the spot. While this usually produces a mark in roughly the right place, it is rarely exact. If the hole is very small, the pen will not go through. Instead, the positions of the holes must be measured, then marked out on the wall or floor with a pencil. If the hole is big enough to accommodate the pen, it is not always inserted perpendicular to the surface - so the marked position comes out in the wrong place. It is also requires a free hand to hold the pen, not always available to persons with only two hands. If hole positions have to be calculated and placed according to measurements, there are multiple opportunities for them to be marked in the wrong places. Plastic screw plugs can absorb a suitable amount of misalignment, but if a spot is badly out of position, the old hole may have to be filled and a new hole drilled next to it. The Challenge Our challenge this month is to devise a simple, accurate method of marking these hole positions. One could consider marking the target spots with a laser, but such equipment is not normally found in the average home tool box - nor should it be. There are those who insert the screws, and tap the heads with a spanner, so that the tip makes a small mark, but this can ruin the points. The solution we offer solves the problem elegantl the problem elegantly and at trivial cost without recourse to any kind of electronics. Once you see it, you will consider it obvious, except that it is innovative enough to be protected by patent. See if you can come up with anything better. Solution Our solution to last month's challenge comes from Stephen Gale who lives on the Isle of Wight. His invention, called Marker Points, comprises small pieces of polyethylene tube. The ends are filled with a mixture of fluorescent paint and oil. They are twisted onto the tips of screws, which may then be inserted and tapped on their heads to release a small dab of paint. This provides a clearly visible pinpoint mark for accurate drilling. Alternatively, Gale offers a kit with a small length of tube filled with paint with a squeeze bulb on one end. One can then insert the tube and squeeze the bulb to achieve the same effect. Prototype samples are available and he is looking for licensees.