NEW! Click here to see an animation of a barge going downstream

NEW! Click here to see an animation of a barge going upstream

Canal locks are a series of gates designed to allow a boat or ship to pass from one level of water to another. Here, after a boat has entered the lock and all gates are secured, the downstream sluices open and water flows through them. When the water level is equal on either side of the downstream gate, water stops flowing through the sluices; the downstream gate opens, and the boat continues on at the new water level.

SOURCE: "Boat Passing Through Canal Lock," Microsoft® Encarta® 97 Encyclopedia © 1993-1996 Microsoft Corporation