Box Joint (Finger Joint)

A box joint (also finger joint, in furniture-scale work) interlocks a series of straight, rectangular "fingers" cut into the ends of two boards meeting at a corner, alternating so one board's fingers fill the gaps in the other's. It's visually similar to a dovetail joint and shares the same large glue-surface advantage over a bare butt joint, but without the dovetail's angled pins and tails.

Because the fingers are straight rather than angled, a box joint has no mechanical wedge resisting the joint being pulled straight apart the way a dovetail's angled tails do -- the joint's strength comes almost entirely from glue surface area, not geometry. That tradeoff is usually a good one: a box joint is dramatically faster to cut, especially with a dedicated box-joint jig on a table saw or router table, since every finger is the same width and spacing rather than individually laid out.

"Finger joint" is also used, confusingly, for the small interlocking zigzag joint that splices short lumber end-to-end into longer structural stock -- a completely different, much smaller-scale joint despite the shared name.