Leonardo da Vinci improved the miter lock for canals by using a movable gate system.
A miter lock has two gates that meet at an angle pointing upstream. Water pressure pushes the gates together against their central seam, helping them remain closed. Leonardo worked on canal engineering in Milan and is associated with improvements to lock gates that made it easier for boats to pass between water levels.
The system allowed a vessel to enter a chamber, after which water could be raised or lowered until the level matched the next section of canal. This avoided the need to haul a boat over an obstacle or build an entire canal at one level. Leonardo’s canal studies also addressed water flow, gates, and navigation.
Leonardo did not invent the basic concept of canal locks, and earlier locks existed in Europe and China. His importance lies in refining practical hydraulic engineering and recording mechanisms in unusually detailed notebooks. A miter lock is sometimes confused with a simple sluice gate, but its paired angled leaves are the defining feature.