Leonardo da Vinci designed canal locks to regulate water levels and help boats move between different elevations.
In Renaissance Milan, Leonardo worked on canal engineering connected with the Navigli system. His studies included lock gates and water-control arrangements that improved navigation by dividing a height difference into controlled stages. A lock uses a chamber between gates: water is added or released until the boat reaches the level of the next canal section, after which the appropriate gate opens.
Leonardo is strongly associated with improvements to the system of canal locks, especially the mitre-gate principle. Mitre gates meet at an angle pointing toward the higher water, allowing water pressure to press them together and help seal the opening. The underlying idea was not created from nothing by Leonardo, since earlier canal engineers had used locks, but his work helped refine and document their engineering.
A canal lock is different from a dam, which primarily holds back water, and from an aqueduct, which carries water across a route. Locks are navigation structures designed to move boats through changing water levels.