How to Measure Twice and Cut Once
Reduce cumulative error by using consistent references, clear marks and test fits.
Work from finished dimensions
Separate finished size from rough stock size. A plan might call for a finished 18-inch panel even though the rough board must be cut longer before jointing or trimming.
Choose one reference
For a group of related parts, mark from the same baseline or reference face whenever possible. Chaining measurements from the previous mark compounds small errors.
Mark the waste side
Use a sharp pencil or marking knife and identify which side of the line is waste. The blade removes material equal to its kerf; cutting directly through the wrong side of a line can make a part undersized.
Batch identical parts
When several pieces must match, use a stop block, story stick or template instead of measuring each one independently.
Dry-fit early
Before glue, test the parts together. Correcting an opening or trimming a stretcher is much easier before adhesive and finish are involved.