BOATsmart! Base de connaissances du Canada 

A lock is a physical structure of gates that enables vessels to travel between two bodies of water that are of different elevations.

Boats enter the lock from one body of water (vessels may enter from each end of the lock but from only one end at a time). Once the gates at the entrance of the lock are closed, the water level within the lock is increased or decreased to match the elevation of the adjoining body of water. When the correct water level has been reached within the lock, the gates are opened and boats are able to travel onwards.

A restricted speed zone is typically found at the entrance to each side of the lock. Obey posted speed limits and watch your wake when approaching a lock. Certain activities such as swimming, fishing, and water-skiing may also be restricted near locks.