An Allen key is a small tool used for driving socket head machine screws. The shape of the Allen key is hexagonal with six straight sides, which can provide an efficient way of quickly driving screws. Using Allen keys can provide you with many benefits as an Allen key is small and light. Hexagonal contact surfaces can be protected from external damage, Allen keys can be used with a headless screw, the bolt can be inserted into its socket using only an Allen key, six contact surfaces between the socket head and the key, a wide range of torque can be applied using only the Allen key, socket heads can be very small.

Allen keys can also save money! By using a single key instead of many reduces tooling costs for the manufacturer and is more convenient for the end user. Many manufacturers have adopted Allen key socket bolts for assembling bicycles or for Self-assembly furniture.