Leonardo da Vinci designed a screw jack to use screw threads for lifting heavy loads.
A screw jack raises a load by converting rotational motion into vertical movement. Leonardo’s mechanical studies included lifting devices based on a threaded screw, a strong frame, and a handle or crank. Turning the screw moved the load gradually upward while providing mechanical advantage.
This principle was especially useful before powered machinery. A threaded mechanism could lift substantial weight with controlled motion, even though the operator had to turn the handle many times. Leonardo examined such mechanisms as part of his broader study of machines, force, friction, and motion.
The screw jack should not be confused with a pulley, which lifts by changing the direction and distribution of tension in a rope. Nor is it the same as a hydraulic jack, which uses fluid pressure. Leonardo’s design belongs to the long history of screw-based lifting machines that later became common in workshops, presses, vehicles, and engineering equipment.