Miter gates are the lock-gate innovation commonly associated with Leonardo da Vinci’s canal designs.
A pair of miter gates meets at an angle pointing upstream. Water pressure pushes the gates more firmly together when the lock chamber is full, helping them resist the force of the water. When the levels on both sides are equalized, the gates can be opened to allow a boat through.
Leonardo worked on canal engineering in Milan and studied locks, water flow, excavation, and navigation. His work is connected especially with the Martesana Canal and improvements to the canal system around the city. The designs show his practical interest in using controlled water levels to overcome changes in elevation.
Leonardo did not invent every principle of canal locks. Earlier pound locks existed in Europe, and the attribution of particular gate forms can be complicated. The key distinction is that miter gates meet at an angle, unlike a single vertical sluice or a lift gate that moves upward.