Leonardo da Vinci designed a screw jack to test and use the force of a screw lifting mechanism.
A screw jack raises a load by converting rotary motion into slow, powerful linear motion. Turning the screw advances a threaded component, allowing a relatively small force applied over a long rotation to lift a heavy object through a short distance. Leonardo’s notebooks contain detailed studies of screws, threads, gears, and mechanical advantage.
The device belongs to his wider investigation of machines that could multiply human effort. Such mechanisms had practical uses in construction, workshops, and military engineering. Leonardo often drew the parts separately and examined how their geometry affected movement, friction, and force transmission.
A screw jack should not be confused with a pulley block, which lifts by redirecting tension in a rope, or a hydraulic jack, which uses fluid pressure. Leonardo’s mechanism depended on the inclined plane wrapped around a cylinder—the basic mechanical principle of a screw. The surviving drawings show an important step in the historical development of lifting machinery, although they do not establish that Leonardo manufactured a standardized jack for commercial use.