Rule 23 of 31 · Chapter V — Joinery and Glue-Ups
Don't fight the clamps
Why this rule exists
Clamps are for holding a good joint closed while glue cures, not for forcing a bad one shut. If you're cranking with all your might to pull a gap together, you're building stress right into the piece, and the moment the clamps come off, that stress fights the joint until something lets go. Heavy clamping pressure also starves a joint of glue and racks an assembly out of square. Clamps persuade; they should never have to wrestle.
In practice
If a joint needs brute force to close, stop and fix the fit instead of leaning harder on the handle. Use just enough clamp pressure to bring the surfaces together with a thin, even squeeze-out, not to bend stubborn parts into place. Use cauls to spread the pressure and protect the wood from dents, and check for square by measuring the diagonals before the glue sets. Add more clamps for even distribution rather than adding raw force through a few.
When it doesn't apply
Slightly springy stock or a gentle bow sometimes needs modest clamping to pull true, and that's fine within reason. Bent laminations and steam-bent parts are clamped hard by design against forms. The caution is against forcing ill-fitting joinery closed, not against every firm clamp; distinguish persuading wood from fighting a bad cut.