Leonardo da Vinci designed a canal lock with two gates to manage water levels.
A lock lets boats move between sections of water at different elevations. The vessel enters a chamber, the gates close, and water is added or released until the boat reaches the level of the next section. Leonardo studied and improved such systems while working on canal engineering in northern Italy.
His designs included mitre gates, whose angled edges press together more tightly as water pressure rises. This arrangement became a valuable improvement in canal construction. Leonardo’s interest in locks was connected with plans to improve navigation around Milan and link waterways more efficiently.
A canal lock is not an aqueduct, which carries water across a gap, nor a water wheel, which extracts energy from flowing water. Leonardo’s contribution was chiefly design refinement and engineering application rather than the invention of every underlying component.