Shiplap Joint

A shiplap joint rabbets the edges of two boards so they overlap when laid side by side, rather than butting flush -- each board's rabbet sits on top of or under its neighbor's, shedding water and hiding the seam better than a plain edge-to-edge butt joint would. It's the traditional joint behind exterior board siding and has become a common interior paneling look as well, usually installed with a small reveal gap left between boards rather than pulled perfectly tight.

Unlike a groove joint capturing a floating panel, shiplapped boards aren't mechanically locked together -- each board is fastened independently, which is exactly what lets a wide wall of shiplap accommodate each individual board's own seasonal movement without splitting.