Not all shop squares are 100% accurate, but plastic drafting squares are. Being transparent, however, they make it tough to see gaps between the square and whatever you are checking. To make the two 90° sides more distinct, mask off 1/2-in.-wide strips at the edges, lightly sand the exposed plastic, clean off the dust with solvent, and spray with gray primer. After the paint dries, the edges will look like steel, turning an inexpensive craft-store square into a precise shop tool.
—DAVID GLEASON, Houston, Pa.
Illustrations by Dan Thornton
From Fine Woodworking issue #296