Leonardo da Vinci designed a miter lock to help boats change water levels in canals.
A canal lock uses gates and a chamber to raise or lower a boat between stretches of water at different elevations. Leonardo’s improvements included angled gates whose inner faces meet in a V shape pointing toward the higher water, a form known as a miter gate.
Water pressure pushes the gates together when the chamber is full, helping them seal. Leonardo applied this principle to canal engineering in northern Italy, including work connected with the canals around Milan. The system reduced the need for large changes in canal height to be crossed in one continuous reach.
Leonardo did not invent the basic idea of a water lock from nothing; earlier canal locks existed. His importance lies in refining practical lock mechanisms and documenting hydraulic engineering with detailed drawings and observations.