One of Da Vinci's most enduring creations was the miter lock. It was immediately put into use in Milan, then spread across the world, and is now used today in almost any waterway. Previous lock designs would take one or two men to move the locks up against the force of gravity. This design utilizes horizontal movements to open and close the lock. The miter lock is the joining of two walls at a 45 degree angle. This allows them to push against each other when faced with the force of oncoming water, making their bond tighter. This invention is just one of the many examples of how Leonardo Da Vinci was a revolutionary engineer of his time. The design was completed in MIlan in 1497. 

Sources:

“The Canal Lock.” Leonardo Da Vinci's Inventions, www.leonardodavincisinventions.com/civil-engineering-inventions/leonardo....

“Leonardo's Miter Gate.” Linda Hall Library, civil.lindahall.org/mitergate.shtml.

Image Source: Linda Hall Library, https://civil.lindahall.org/mitergate.shtml