Leonardo da Vinci improved the canal miter lock with angled gates that seal against each other.
A lock allows boats to move between stretches of water at different elevations. In a miter lock, two gates meet at an angle pointing upstream. Water pressure pushes the gates together, helping them resist the force of the higher water level. Leonardo studied and refined this arrangement while working on canals in northern Italy.
His canal work is especially associated with the Naviglio di San Marco system in Milan. The design reduced the space and water-handling difficulties involved in raising or lowering boats through a waterway. The basic miter-gate principle later became standard in canal engineering.
A miter lock is not simply a sluice gate. A sluice controls water flow through an opening, whereas a navigation lock is a chamber with gates at both ends that changes a vessel’s elevation.