Leonardo da Vinci designed a miter lock using two gates meeting at an angle to control canal water.
A miter lock has paired gates whose pointed meeting edge faces the higher water level. Water pressure pushes the gates together, helping them seal the chamber. By opening or closing the gates in sequence, boats can move between sections of canal with different water levels.
Leonardo studied canal engineering in northern Italy, especially around Milan, where waterways were important for transport, irrigation, and construction. His notebooks contain designs for locks and other hydraulic structures, including mechanisms intended to make water management more reliable.
Leonardo did not invent every principle of canal locks, and earlier lock systems existed in Europe and Asia. His importance lies in the detailed engineering studies he made of hydraulic problems and in the improvements he proposed for canals and navigation.