The lock is made up of levers (usually made out of non-ferrous metals). Each lever needs to be lifted to a specific height by the key in order for the locking bolt to move. Typically, the belly of the lever is cut away to various depths to provide different combinations, or the gate is cut in a different location, to provide differs. A lever will have "pockets" (or "gates") through which the bolt "stump" (or "post" or "fence") moves during unlocking.