Leonardo da Vinci designed a screw jack to raise heavy loads with a threaded mechanism.
A screw jack converts rotational motion into slow, powerful linear movement. Turning a handle rotates a threaded screw, which drives a lifting surface upward or downward. Leonardo’s notebooks contain studies of screw-based lifting devices among his broader work on machines, construction, and military engineering.
The principle was especially useful before powered cranes and hydraulic lifts became common. Mechanical advantage allowed a person to move a load much heavier than could be lifted directly, although the trade-off was slow movement. Leonardo’s interest lay in arranging gears, screws, and supports into compact, controllable machines.
The screw jack should not be confused with a pulley crane, which lifts by tension in ropes, or with a hydraulic jack, which uses pressurized fluid. Leonardo’s proposed device belongs to the screw family of lifting mechanisms. Later jacks became important in vehicles, workshops, construction, and engineering.