Leonardo da Vinci designed a screw jack to lift heavy loads using the mechanical advantage of a spiral screw.
A screw jack converts rotary motion into controlled vertical movement. When a handle turns the screw, the threaded mechanism raises or lowers a platform or load in small, precise increments. Leonardo studied this principle in his designs for lifting machines and construction equipment, applying it to the practical problem of moving heavy materials.
The design is distinct from a pulley crane, which uses ropes and wheels, and from a hydraulic press, which depends on fluid pressure. A screw jack is especially useful when slow, accurate lifting matters more than speed. Its mechanical advantage comes from the long distance traveled by the handle compared with the short vertical distance gained by the load.
Leonardo did not invent the screw itself, which was known in antiquity. His contribution was the systematic development and application of screw-based mechanisms in Renaissance engineering drawings.