Leonardo da Vinci improved the canal device known as a miter lock.
A miter lock uses two gates that meet at an angle pointing upstream. Water pressure pushes the gates together, helping them seal. Leonardo applied this principle to canal locks in Milan, where differences in water level made navigation and water management technically demanding.
Leonardo is often credited with improving canal-lock mechanisms rather than inventing the entire idea of water locks. His studies addressed practical details such as gates, channels, and the movement of boats between different elevations. The Naviglio di San Marco lock in Milan is traditionally associated with his work.
A lock is not the same as a sluice gate. A lock raises or lowers boats between water levels, while a sluice mainly controls the flow of water. Leonardo’s canal studies show how his engineering combined hydraulic theory with local transport and construction problems.