Rule 22 of 31 · Chapter V — Joinery and Glue-Ups
Glue is not a substitute for fit
Why this rule exists
There's a myth that modern glue is so strong it fills gaps and fixes sloppy joints. It doesn't. Wood glue is strongest in a thin film between two well-mated surfaces; a gap packed with glue is a weak, brittle line that fails under stress. A joint that fits crisply barely needs the glue to be strong. Chase a good fit with your saw and chisel, and the glue just makes permanent what already fit. Sloppy cuts don't glue their way to strength.
In practice
Cut and pare joints until the mating surfaces meet cleanly under firm hand pressure, snug but not so tight they split the wood or need pounding home with a mallet. Test the fit dry every time before you commit. Where a gap sneaks in, stop and fix the joint rather than trusting glue to bridge it invisibly. Use glue sparingly on well-fit surfaces; the squeeze-out should be a modest, even bead all along the joint, not a flood hiding a bad cut.
When it doesn't apply
Gap-filling adhesives like epoxy and polyurethane genuinely do bridge small voids and suit outdoor or ill-fitting repairs where perfect joinery isn't possible. And in rough construction, a bead of construction adhesive forgives a lot. The rule is about ordinary wood glue in furniture joints, where fit carries the strength.