Leonardo da Vinci sketched a screw jack, a mechanical lifting device that uses a threaded screw.
A screw jack raises a load by converting rotary motion into vertical movement. Turning the screw advances a threaded component, allowing a relatively small input force to lift or hold a much heavier object. Leonardo studied screw-based mechanisms in his notebooks and applied the principle to machines for lifting, adjusting, and supporting loads.
The screw jack belongs to a long history of mechanical lifting technology. Ancient engineers used screw mechanisms, and later jacks became common in construction, workshops, and vehicles. Leonardo’s importance lies in his detailed analysis and drawings of how such mechanisms could be integrated into practical machines.
This device is sometimes confused with a simple pulley, but the mechanisms work differently. A pulley redirects or multiplies force through a rope, while a screw jack relies on the mechanical advantage of a threaded spiral and can hold a load securely when properly designed.