Leonardo da Vinci improved the canal lock with paired miter gates that could manage changing water levels.
A lock lets boats move between sections of canal at different elevations. The chamber is closed, then water is added or released until the water level matches the next section. Angled miter gates meet in a point facing the higher water pressure, helping them stay shut.
Leonardo worked on canal engineering in northern Italy and is associated with improvements to lock gates, including the use of mitred doors. Such designs made navigation more practical on canals where a simple opening could not safely hold back a difference in water level.
Leonardo did not invent the basic idea of a canal lock. His contribution belongs to the refinement of hydraulic engineering, especially the design and operation of gates used to control water and boat movement.