What type of lock did Leonardo da Vinci improve for canal water-level control?

Leonardo da Vinci improved the miter gate lock for canal water-level control.

A miter gate lock uses two gates that meet at an angle pointing upstream. Water pressure pushes the gates together, helping them seal the opening when the chamber holds a higher water level. Leonardo studied and improved canal-lock mechanisms during his work as an engineer in northern Italy.

His improvements are associated especially with the canal system around Milan. The gates allowed boats to pass between waterway sections with different elevations, solving a major problem for inland navigation. Leonardo’s engineering notes examined gates, channels, water flow, and the practical operation of locks.

Leonardo did not invent the general idea of a canal lock. Earlier pound locks existed in Europe, and the basic principle was already known. His contribution was the refinement and application of lock technology, including the distinctive angled gates. Modern navigation locks still use miter gates because hydraulic pressure helps keep them closed.