Leonardo da Vinci designed canal-lock systems to move boats between waterways at different elevations.
During his work in Milan, Leonardo studied canals, irrigation, and methods of improving navigation. His drawings include lock arrangements with chambers and gates that could admit or release water. A boat entering the chamber could be raised or lowered as the water level changed, allowing it to continue along a canal with a difference in height.
A lock is not the same as a dam or a simple sluice gate. The defining feature is the enclosed chamber between gates. By controlling water in that chamber, canal builders can change a vessel’s elevation without moving it overland.
Leonardo did not invent every principle of the canal lock: earlier examples existed in Europe and China. His importance lies in his detailed engineering studies and improvements to canal systems, especially around Milan. His drawings show how closely he connected hydraulic engineering with transportation and urban infrastructure.