Leonardo da Vinci designed a screw jack to lift heavy loads through mechanical advantage.
A screw jack converts rotation into a slow, powerful vertical movement. Turning the screw advances a threaded component and raises the load, allowing a person to lift more than would be possible by direct force alone. Leonardo studied versions of this mechanism in his engineering notebooks.
Screw-based lifting devices were not unique to Leonardo. Ancient and medieval engineers already used screws, winches, pulleys, and treadwheels. Leonardo’s importance lies in his detailed observation, improvement, and systematic recording of machines.
The device is sometimes confused with a crane. A crane is a complete lifting system that may use a boom, ropes, and pulleys; a screw jack is a compact lifting mechanism that raises a load directly through a threaded screw.