Leonardo da Vinci improved canal navigation with a miter lock using paired hinged gates that meet at an angle.
A navigation lock lets boats move between waterways at different elevations. The lock chamber is closed by gates, filled or emptied, and then opened at the other end. Leonardo’s improvements are associated with the canal system of Milan, especially the Naviglio di Martesana, where reliable control of water levels was essential.
Miter gates are arranged so water pressure helps press their meeting edges together against the gate frame. This made them more effective than simpler gates for holding back water. Leonardo’s work built on earlier canal technology rather than inventing the entire idea of locks from nothing.
The device is often confused with a sluice gate. A sluice controls water flow through an opening, while a navigation lock changes a boat’s elevation between water levels. Leonardo’s canal engineering also included studies of channels, basins, and water-control mechanisms.