Socket screw wrench set - Free image download
Image description >> A silver hex key set in a variety of sizes is a very convenient set of tools to have. This tool of hexagonal shape is used to drive screws and bolts that have a hexagonal socket in the head. It is commonly called an allen key, but this name is a registered trademark and its generalized name use is discouraged by the Apex Tool Group, LLC; the standard name used in catalogs is hex key. The hex key is a great little tool because it is small, light, simple to use, and very cheaply manufactured. There are six contact surfaces between the hex key and the screw, so even very small bolts can be easily used, and the key is L-shaped, so either end of the tool can be used, making it an asset in terms of reach and torque.