An Allen screw, also known as a hex screw or a socket head screw, is a type of fastener used to secure objects together. It features a hexagonal socket in the head, which requires a matching Allen key or wrench to tighten or loosen the screw. Some other common synonyms for an Allen screw include wrench screw, hexagonal screw, and socket screw. However, depending on the context and industry, there may be other terms used to refer to this type of screw, such as hex head bolt, Allen bolt, or cap screw. Regardless of the terminology used, Allen screws are widely used in a variety of applications, from construction and engineering to automotive and electronics.