A
lock is a device used for raising and lowering
boats,
ships and other
watercraft between stretches of water of different levels on river and canal
waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a
caisson lock, a
boat lift, or on a
canal inclined plane, it is the chamber itself (usually then called a
caisson) that rises and falls.