I have some sheet-rock to hang and I always have trouble locating the electrical boxes after I have put the sheet-rock over the top of it. I thought that this target system would be an easier way of locating the electrical boxes once the sheet rock is placed over them.

It consists of a magnetic target designed to fit inside the electrical box and a magnetic face-plate that aligns with it through the sheet-rock. The face-plate is sized to the opening that is needed to be cut - making it easy to accurately cut the opening.

The OpenSCAD file is written to be parametric and easy to adapt to different electrical boxes or magnets. All of the important parameters are listed at the top of the file. Care may be needed if the magnets get too big or too thick.

The default parameters are set for a typical electrical box that I purchased at Ace, so should work for most others. The magnets are 18mm Super Magnets (Neodymium) - also from Ace. I tried an earlier prototype with 8mm magnets, these didn't have sufficient power to hold the face-plate on through the sheet-rock.

There are three openings for magnets, but I've found that two are sufficient for the task. I alternated the polarity of the magnets on my version to ensure that the face plate would only orient itself in one direction. The magnets are glued in with a dab of super-glue and clamped in place until dry.

You can print multiple targets to handle multiple electrical boxes or double or triple boxes.

To use the targets: mount your electrical box and wire it. Place the target in the electrical box, flush to the surface. Install the sheet rock. Then locate the position with the face-plate. Mark the outline, cut and clear the opening.