A French cleat is a way to hang heavy items onto walls. A single piece of wood is split in two at a angle. Alternatively, two pieces of wood are cut at angles to fit one on top of the other. Use a French cleat for mounting shelves and bookcases on a wall.
The Lattice Window Box w/ Cleat Mounting System. You simply mount the cleat to your wall and hang the box off the cleat. The cleat is recessed inside the back of the box wall for easy mounting flush to your wall.