Leonardo da Vinci’s canal device was designed to control water flow between two water levels.
Leonardo is associated with improvements to the mitre lock, a canal lock using two angled gates that meet in a V shape pointing toward higher water. Water pressure helps press the gates together, improving the seal when the higher-level side pushes against them.
A lock allows boats to travel between different elevations. Gates close a chamber, water is added or released until its level matches the next section, and the boat then moves onward. This principle transformed navigation in canals and reduced the need to haul boats over uneven terrain.
Leonardo worked on canal and hydraulic engineering in northern Italy, including projects connected with Milan. The underlying lock technology predates him, so he should not be credited with inventing the canal lock itself. His contribution lies in studying, refining, and applying hydraulic mechanisms with unusually detailed engineering drawings.