Measure Between Miters Exactly With a Pair of Test Blocks

The Problem

A piece with a mitered long point on each end can't be measured directly — there's no square face to hook a tape on, and reading to a knife-edge point invites a sixteenth of error at both ends. On tongue-and-groove or shiplap runs, where every piece has to land tight, those sixteenths show.

The Technique

1. Cut two test blocks from the same stock, with the same miter as the workpiece, each trimmed to a known dimension — 10 inches from the long point to the square end.
2. Set a block into each end of the run, long points seated where the workpiece's long points will land.
3. Measure square-end to square-end between the two blocks. That's a clean hook-and-read measurement.
4. Add the two block lengths. In the reel: 32 between blocks, plus 10 and 10, gives 52 long-to-long.

The blocks convert an unmeasurable knife-to-knife dimension into an ordinary tape pull plus known constants — and they're reusable for the whole job.