A windlass is an apparatus for moving heavy weights. Typically, a windlass consists of a horizontal cylinder (barrel), which is rotated by the turn of a crank or belt. A winch is affixed to one or both ends, and a cable or rope is wound around the winch, pulling a weight attached to the opposite end.
Windlasses are vital in the operation of almost all locks on the British Inland Waterways. They can also be used for water wells. The oldest depiction of a windlass for water wells comes from the Book of Agriculture published in 1313 by the Chinese official Wang Zhen (official) (fl. 1290–1333) of the Yuan Dynasty, while in Medieval Europe they were used by about 1425 AD. Some crossbows of Medieval Europe also employed a windlasses as a cocking mechanism.