Find an Unknown Angle With a Scrap Board and a Pencil

The Problem

Sooner or later a job hands you an angle nothing on your square matches — a wall out of square, an old framing member, a custom detail. Guessing at the miter saw burns boards one degree at a time.

The Technique

1. Take a straight scrap board and lay it against the piece carrying the unknown angle.
2. Scribe along the other side, transferring the angled face onto the scrap.
3. The scribed line on the scrap is the angle. Cut it, check the fit against the work, and use the scrap to set your saw or mark your workpiece.

In the reel the mystery angle turns out to be a degree and a half — the kind of nearly-square-but-not angle that's invisible to the eye and obvious in the joint. Watch the video for the exact setup; the scribe pass takes seconds.