Screws are yet another simple machine used since antiquity. They tend to consist of a cylindrical rod with one or more helical spiraling threads or ridges on the outside.
These ingenious mechanical engineering innovations convert rotational motion into linear force. Screws can also be perceived as a very narrow inclined plane, or ramp, that is wrapped around the cylinder.
Famous early examples include the Archimedes screw that was used an early form of a water pump.
Screws, like ramps, levers, and pulleys, allow a force to be amplified. In the case of the screw, it provides a mechanical advantage for converting a small torque (rotational force) into a large axial force on a load.
Its mechanical advantage changes depend on the distance between the screw's threads, aka pitch. They are widely used today as fasteners or as basic pumps, presses and as precision devices.