You can think of a screw as an inclined plane wrapped around an axle. The ancient Greeks used a screw to lift water. Screws and bolts are also used to fasten two pieces of wood, plastic, or metal together.

Screws have a large mechanical advantage, and thus the distance the screw thread moves in its circular motion is much larger than the distance the screw moves into the material. Therefore the force the screw or bolt exerts to hold the material together is large in comparison to the torque used to turn the screw. Screws and bolts are also inefficient machines because of the friction between the screw and material, or between the metal of the bolt and nut.