Leonardo da Vinci designed a miter lock with two gates to move boats between different water levels.
A miter lock uses two gates that meet at an angle pointing toward the higher water. Water pressure pushes the gates together, helping them resist the force of the water. Leonardo studied and improved canal-lock mechanisms while working on water-management projects in northern Italy.
His designs are associated especially with the Milan canal system. Leonardo’s notebooks show careful attention to gates, channels, water flow, and the practical movement of boats. The lock concept allowed a vessel to enter a chamber, have the water level changed, and then leave at the new elevation.
Leonardo did not invent the general idea of a navigation lock, and similar devices existed before his work. His importance lies in analyzing and refining hydraulic engineering. A common mistake is to call every Leonardo canal drawing a new invention; many were studies or improvements of existing technology.