Leonardo da Vinci designed a mitre gate for canals to control water levels.
A mitre gate consists of two hinged leaves that meet at an angle, usually pointing upstream. Water pressure pushes the leaves together, helping the gate seal the opening. This principle became important in canal locks, where gates separate sections of water at different elevations.
Leonardo studied canal engineering in northern Italy, especially around Milan. His notebooks contain drawings of locks and mechanisms intended to make water transport more efficient. The famous double-leaf arrangement is associated with his improvements to canal gates, although similar water-control ideas had earlier precedents.
Leonardo did not invent canals or the basic idea of a lock. His contribution was to observe, refine, and document practical engineering solutions. Mitre gates remain common in canal and navigation infrastructure, making this one of his more enduring engineering concepts rather than merely a fanciful machine.