Dovetail
A flared tail that only pulls tighter the harder you tug.
The dovetail is the joint that can't be pulled apart in one direction — the flared tail and socket interlock, and the harder you tug, the tighter they bind.
How to cut it
tails cut first, saw to the knife line pins transfer with a marking knife, not a guess angles 1:7 softwood, 1:8 hardwood test dry-fit, then pare the proud spots
Where it lives
Drawers, chests, and anywhere two boards meet at a corner and have to stay married for a hundred years.