Leonardo da Vinci designed a canal lock to let boats bypass a change in canal level.
Leonardo worked on hydraulic engineering in northern Italy and is associated with improvements to canal-lock designs, especially for the Naviglio di San Marco in Milan. A lock uses chambers and gates to raise or lower a boat between waterways at different elevations. By filling or emptying the chamber, boats can pass without dragging over a steep barrier.
Leonardo did not invent the basic idea of the canal lock from nothing; earlier locks existed in Europe. His contribution was to study and refine practical details, including gates, water flow, and canal navigation. This distinction matters because popular accounts sometimes call him the inventor of the lock outright. Leonardo’s hydraulic notebooks also cover canals, mills, pumps, and flood control, showing that his engineering interests extended well beyond military machines.