Leonardo da Vinci designed a canal lock using paired gates to control water levels and boats.
His lock design was associated with the Naviglio di San Marco in Milan. The system used a chamber between gates, allowing water to be raised or lowered so a boat could move between sections of canal at different elevations. This made navigation possible where a single level waterway could not continue smoothly.
Leonardo is often credited with improving the mitre lock, whose two gates meet at an angle pointing against the higher water. Water pressure helps press the gates together and improve the seal. The exact history of the lock includes earlier engineering work by others, so Leonardo should be described as an important designer and improver rather than the sole inventor of every canal lock.
His studies connected hydraulic engineering with urban transport. The canal lock is distinct from Leonardo’s proposed hull designs, which addressed ship safety rather than changes in water level.