Leonardo da Vinci improved the canal lock with a hinged gate and a watertight chamber.
A canal lock lets boats move between waterways at different elevations. It works by placing a vessel inside a chamber, closing gates at both ends, and raising or lowering the water level until the boat can continue. Leonardo studied and refined this principle while working on canals in northern Italy.
His designs are associated especially with the mitre gate, whose two leaves meet in a V shape pointing toward higher water. Water pressure pushes the gates together, helping them seal. Leonardo also developed practical details for operating gates and managing water flow.
Locks existed before Leonardo, so he did not invent the basic idea. His contribution was the improvement of a useful engineering system. The Naviglio di San Marco in Milan is commonly linked with his canal work, although the history of individual lock projects is complex.