canal lock: side view

upper gate

Watertight door or pair of doors made of wood or metal that open when the water levels between the lock-chamber and the upper level are the same.

lower gate

Watertight door or pair of doors made of wood or metal that open when the water levels between the lock-chamber and the lower level are the same.

upper level

Part of the lock at the upstream end of the lock-chamber.

lock-chamber

Central part of the lock where the water level is raised and lowered depending on the heading of the ship.

lower level

Part of the lock at the downstream end of the lock-chamber.

flow

Natural current moving down the grade from upstream to downstream.