A flat, usually rectangular structure composed of a rigid material, such as wood, glass, or metal, fixed at right angles to a wall or other vertical surface and used to hold or store objects.
The contents or capacity of such a structure.
Something, such as a projecting ledge of rock or a balcony, that resembles such a structure.
A reef, sandbar, or shoal.
Bedrock.
off the shelf From ready-made merchandise in stock: supplies that were available off the shelf.