Leonardo da Vinci improved canal engineering with a miter lock using hinged gates.
A miter lock has two gates that meet at an angle pointing upstream. Water pressure pushes the gates together, helping them seal the opening. Leonardo used this principle in canal-lock designs associated with Milan, where waterways had to overcome differences in elevation.
The lock allowed boats to move between water levels without requiring a single long channel at one height. Operators could close the gates, adjust the water level, and then open the opposite side. Leonardo’s work included improvements to canal gates and lock mechanisms rather than the invention of every element of the canal system.
The design is sometimes confused with a drawbridge because both use hinged structures, but a canal lock controls water level. Leonardo’s engineering notebooks show sustained interest in Milan’s canals, navigation, irrigation, and hydraulic power.