Cleat

A cleat is a strip of wood (or metal) fastened to a surface specifically to support, hang, or align something else against it -- a ledge screwed inside a cabinet to carry a shelf's weight without needing a full dado, or a wall-mounted batten a picture frame or cabinet hangs from. A French cleat -- two matching strips, each cut at a mirrored 45-degree bevel, one fixed to the wall and one to the back of whatever's being hung -- is a specific, especially common cleat system that lets a heavy cabinet or shop fixture be hung and removed from the wall easily, self-aligning and self-locking under its own weight as the two bevels engage.