Picture by Jacob

A screw is a simple machine that is made from another simple machine.  It is actually an inclined plane that winds around itself.  A screw has ridges and is not smooth like a nail.  Some screws are used to lower and raise things.  They are also used to hold objects together.

The screw has a spiral lines around it a screw helps you work buy you screwing boards things like that with a screw driver or a drill.