Leonardo da Vinci designed a mitre lock to help boats pass between different water levels.
Leonardo worked on canal engineering in northern Italy and is associated with improvements to lock gates. A mitre lock uses two gates that meet in a V shape, with the point directed toward the higher water. Water pressure helps press the gates together, creating a tighter seal. By opening and closing the gates in sequence, boats can move between canal sections at different elevations.
The principle was not wholly invented by Leonardo; canal locks and related gates existed before his work. His contribution was to study, refine, and apply hydraulic engineering ideas in practical canal systems. His designs are linked especially with the canals around Milan and the Naviglio systems.
A mitre lock is different from a simple sluice gate. A sluice controls water flow through an opening, while a lock chamber temporarily holds a boat and changes its water level. This distinction explains why the answer is a specific gate type.