A screw is a type of fastener that consists of a cylindrical shaft with a helical ridge, known as a thread, wrapped around it. Screws are used to hold objects together by creating a strong connection when turned into materials like wood or metal. They come in various sizes and types, each designed for specific applications. Screws are typically made from materials such as steel, stainless steel, or plastic, depending on their intended use. The head of a screw can be shaped in different ways, such as flat, Phillips, or hex, allowing for various tools, like screwdrivers or wrenches, to be used for installation and removal.