Guard locks, movable dams, and barriers are used for closing off river arms, sealing canal sections, or protecting a canal section from the river or safeguarding an infrastructure, usually with a significant difference in water levels.

Most ship lifts have a barrier in the upper section to be able to drain the upper chamber of the ship lift, but also as protection in case the ship lift malfunctions for any reason. After a major accident occurred with the gate at the Arzviller inclined plane on the Canal de la Marne au Rhin, causing the entire feeder canal to empty into the valley downstream of the inclined plane, an additional gate was installed near the inclined plane itself.