Leonardo da Vinci designed a miter lock for canals to control water levels.
A miter lock uses two gates that meet at an angle pointing toward the higher water. Water pressure pushes the gates together, helping them seal the opening. When the water levels on both sides have been equalized, the gates can be opened safely and a boat can pass between different canal levels.
Leonardo’s canal engineering work in northern Italy included improvements to navigation systems and lock gates. His designs were part of a broader tradition of hydraulic engineering rather than an isolated invention created without predecessors. The miter-gate principle became especially important because it made canal locks stronger and more practical.
This mechanism is a waterway lock, not a security lock for a door. Leonardo also designed canal improvements, lifting devices, and water-management machinery, so references to his “locks” can otherwise be ambiguous. The defining feature here is the pair of angled gates that meet at a point.