Leonardo da Vinci added miter gates to a canal lock design to control water levels.
Miter gates are paired gates that meet at an angle pointing upstream. Water pressure pushes the gates together against their angled meeting seam, helping them resist the force of the water. Leonardo studied and improved canal-lock mechanisms while working on hydraulic projects in northern Italy, including systems associated with Milan’s waterways.
A lock allows boats to move between stretches of canal at different elevations. The gates close a chamber, and water is added or released until the boat reaches the level of the next section. Leonardo did not invent the general idea of canal locks, but his drawings show detailed attention to gates, channels, and the practical control of water.