Leonardo da Vinci improved canal engineering with the miter lock, whose two angled doors meet in a point.
In a miter lock, the gates close at an angle so water pressure pushes them more tightly together. This makes the gates self-sealing when the chamber contains water at a higher level on one side. Leonardo used the principle in designs for canals around Milan, where locks were needed to manage changes in elevation and support navigation.
Leonardo did not invent the basic idea of a canal lock, and earlier locks existed in Europe. His contribution was the refinement and application of practical lock mechanisms, including improved gate arrangements and operating details.
A miter lock is different from a single sluice gate. A lock chamber raises or lowers boats between water levels, while a sluice gate mainly controls the flow of water. Leonardo’s canal studies connected civil engineering, hydraulics, transport, and urban planning.