Lock (Waterway)

An enclosed section of a waterway in which the water level is changed to transfer vessels between different levels.

A chamber is closed by gates and filled or emptied through sluices, culverts or pumps until its level matches the waterway ahead. Locks range from manually operated canal structures to large controlled systems for ships, and may be arranged singly, in flights or with intermediate gates.

Approach signals, priority, line use and engine rules vary locally. Crews must allow for turbulence, changing freeboard, projections, slippery walls and lines that can jam or hang up as the vessel rises or falls; local instructions and lock-keeper directions take precedence.