Leonardo da Vinci improved the canal lock by using paired miter gates that close against each other.
A miter lock has two gates meeting at an angle that points upstream. Water pressure pushes the gates together, helping them resist the force of the water when the levels differ. Leonardo studied and improved canal locks during his work in northern Italy, where navigable waterways connected cities, mills, and agricultural areas.
The basic pound lock was already known before Leonardo, so he did not invent the general idea of raising boats between water levels. His contribution was associated with improvements in gate design, water control, and canal engineering. Leonardo’s notebooks contain studies of locks, sluices, channels, and hydraulic machinery. The term “miter lock” is sometimes written “mitre lock,” especially in British English. It describes the gate arrangement, not the entire canal or the boat that passes through it.