Leonardo da Vinci is associated with improving the miter lock, a canal gate design for controlling water levels.
A miter lock uses two gates that meet at an angle pointing upstream. Water pressure pushes the gates together, helping them seal the opening. Leonardo studied canal engineering in northern Italy and is credited with developing practical improvements to lock gates, including designs used in Milan's waterways.
The principle is valuable because it allows boats to move between sections of canal with different water levels. Operators close the gates, fill or empty the chamber, and then open the opposite end. This makes a staircase of water levels manageable for navigation.
A miter lock is not the same as a simple sluice gate. A sluice controls flow through an opening, while a navigation lock uses paired gates and a chamber to raise or lower boats.