Leonardo da Vinci designed a screw jack to raise heavy loads by winding a screw.
A screw jack converts rotary motion into controlled vertical movement. Turning a handle advances a threaded screw through a fixed or moving component, producing lifting force over a relatively short distance. Leonardo’s mechanical studies examined this principle as part of his broader interest in gears, threads, and machines that multiply human effort.
The device would have been useful for lifting or positioning heavy objects more precisely than a simple lever. Its advantage is mechanical control: a person can raise a load gradually and hold it in place without needing to lift the entire weight directly.
Leonardo did not invent the general idea of the screw. Ancient and medieval engineers already used screws and screw presses. His contribution was to develop and document sophisticated mechanical arrangements, including lifting devices, in a period when systematic machine design was becoming increasingly important.