Leonardo da Vinci studied the mitre lock for controlling water levels in canals.
A mitre lock uses two gates that meet at an angle pointing upstream. Water pressure pushes the gates together, helping them seal when the lock chamber contains a higher water level. By opening and closing the gates in sequence, boats can move between sections of canal at different elevations.
Leonardo worked on canal engineering in northern Italy, especially around Milan, where waterways supported transport and irrigation. His notebooks record detailed observations about water flow, gates, channels, and construction. He is often credited with improving canal-lock designs, although the broader history of mitre gates predates Leonardo and cannot be attributed entirely to him.
The mitre lock is sometimes confused with the pound lock as a whole. A pound lock is the complete chamber system; mitre gates are the characteristic angled gates used at its ends. Leonardo's contribution lies in study and refinement rather than the invention of every underlying principle.