Leonardo da Vinci improved the miter lock design for the Naviglio di San Marco in Milan.
A miter lock uses two gates that meet at an angle pointing upstream. Water pressure pushes the gates tightly together, helping them resist the force of the water when the levels differ. Leonardo worked on canal engineering in Milan and is credited with improvements to the lock gates used on the Naviglio di San Marco.
Leonardo did not invent the basic idea of canal locks, and earlier water-control systems existed in Europe and China. His contribution was practical refinement: his drawings examine gates, channels, and ways to move boats through changing water levels. The Naviglio di San Marco formed part of Milan’s canal network, which supported transport and linked the city with larger waterways.