LOCK, or Weir, in inland navigations, the general name for all those works of wood or stone made to confine and raise the water of a river: the banks also which are made to divert the course of a river, are called by these names in some places. But the term lock is more particularly appropriated to express a kind of canal enclosed between two gates; the upper called by workmen the sluice gate, and the lower called the flood gate. These serve in artificial navigations to confine the water, and render the passage of boats easy in passing up and down the stream. See CANAL.