Leonardo da Vinci designed a canal lock to carry boats over changes in canal elevation.
A canal lock is a chamber with gates at both ends. Water is added or released so a boat can rise or descend between two sections of water at different levels. Leonardo studied and improved lock mechanisms while working on canal projects in northern Italy, especially around Milan.
His designs included mitre gates, whose angled surfaces press together more tightly as water pressure increases. This was an important engineering detail because it helped the gates resist leakage. Leonardo also considered sluices and methods for controlling the movement of water.
Leonardo did not invent the general idea of a lock from nothing; earlier forms of canal locks existed in Europe. His importance lies in analyzing and refining hydraulic machinery and documenting practical improvements. The system differs from a dam, which blocks or stores water, and from an aqueduct, which carries water across a gap rather than lifting boats between canal levels.