Leonardo da Vinci developed a miter lock design for canals to overcome changes in water level.
A miter lock uses two gates that meet at an angle pointing upstream. Water pressure helps press the gates together, creating a seal when the lock chamber holds water. By opening and closing the gates in sequence, boats can move between canal sections at different elevations without navigating a dangerous drop.
Leonardo worked on canal engineering in northern Italy and studied ways to improve navigation around Milan. His canal-lock designs included practical details for controlling water and operating gates. The basic principle had earlier roots, but Leonardo refined and documented mechanisms that made canal transport more efficient.
Leonardo is often credited too broadly with inventing canal locks themselves. Earlier pound locks existed in Europe before his work. His importance lies in developing and recording sophisticated designs, including the distinctive miter-gate arrangement associated with many modern locks.