Leonardo da Vinci designed a miter lock with interlocking angled gates for water control.
The miter lock is a canal-lock arrangement in which two gates meet at an angle pointing toward the higher water level. Water pressure pushes the gates together, helping them resist the force of the water. Leonardo studied and improved canal engineering while working in northern Italy.
His canal projects were particularly associated with Milan and the Naviglio system. The invention commonly linked to him is the mitred, or miter, lock gate, which made it possible to manage differences in water level more efficiently than simpler arrangements.
Leonardo did not invent canals or every form of lock. Earlier water-control systems existed, and later engineers refined the design. The surviving drawings and historical accounts instead show his role in developing practical canal machinery and applying geometry to hydraulic engineering.