Leonardo da Vinci developed a miter lock for canals to help boats pass between different water levels.
His canal work in Milan included improvements to lock gates, especially the angled gates now known as miter gates. Two gates meet in a point facing the higher water level, so water pressure helps press them together and seal the opening. By filling or emptying the lock chamber, boats can move safely between sections of canal at different elevations.
Leonardo did not invent the basic canal lock from nothing. Earlier locks existed in China and Europe, and the Milanese canal system already used water-control structures. His contribution was the refinement and application of engineering ideas to improve navigation and water management.
The term miter lock is sometimes confused with a simple sluice gate. A sluice controls or releases water through an opening, whereas a navigation lock is a chamber with gates at both ends that raises or lowers boats.