Leonardo da Vinci designed canal locks to regulate water levels and help boats pass between sections of a waterway.
His work on Milan's canals included detailed studies of gates, chambers, and water flow. A lock allows a vessel to enter an enclosed chamber, where the water level is raised or lowered before the vessel continues. This makes navigation possible when parts of a canal lie at different elevations.
Leonardo is strongly associated with improvements to the canal-lock system, especially the mitre gate. The angled gates meet in a V shape that points toward the higher water, allowing water pressure to help hold them shut. The Naviglio di San Marco in Milan is connected with this history.
Leonardo did not invent every form of lock from nothing; earlier water-control systems existed. His importance lies in refining and documenting practical hydraulic engineering for canals and navigation.