Leonardo da Vinci designed a screw jack to produce a strong pulling or lifting force using a screw mechanism.
A screw jack converts rotation into slow, powerful linear movement. Turning a handle rotates a threaded screw, and the matching thread advances the load-bearing part of the device. Leonardo's mechanical drawings explored this principle for lifting and moving heavy objects, an important requirement in construction, military engineering, and workshop machinery.
The advantage of a screw jack is mechanical advantage: a relatively small effort applied over a long circular path can produce a much larger force over a short vertical distance. The trade-off is speed, because the load moves only a small distance for each turn. Friction also helps the mechanism hold a load in place.
Leonardo did not originate the screw as a machine principle. Ancient engineers used screws and screw presses, and later jacks became common tools. His drawings are significant because they present a systematic Renaissance analysis of threaded mechanisms and their uses in lifting.