Leonardo da Vinci’s hinged-gate canal device was 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 the chamber. Leonardo studied and improved canal-lock designs in Milan, where controlled water levels were important for navigation and irrigation.
His work is associated especially with the San Marco basin and the Naviglio canals. By separating sections of waterway into lock chambers, boats could be raised or lowered between different water levels without requiring a single continuous slope.
Leonardo did not invent the basic canal lock from nothing; earlier locks existed in Europe. His importance lies in detailed engineering studies and improvements to practical water-control systems. A miter lock is therefore more specific than the broader term “canal lock.”