Leonardo da Vinci improved the mitre lock, a canal gate system used to control water levels and allow boats to pass between sections of different elevation.
A mitre lock uses two gates that meet at an angle pointing toward the higher water. Water pressure pushes the gates together, helping them resist the force of the water. Boats enter the chamber, the gates close, and the water level is raised or lowered before the opposite gates open.
Leonardo studied and improved canal locks during his work in northern Italy. His engineering notes addressed canals around Milan and methods for moving boats through changing water levels. The improvements are associated with practical canal engineering rather than a completely new invention of the lock itself.
A mitre lock is not simply a sluice gate. A sluice controls or releases water through an opening, whereas a lock chamber changes a boat’s elevation. This distinction explains why the lock was important for inland navigation.