Allen Key Wrench

A hex key or Allen key or wrench (also known by various other synonyms) is a tool of hexagonal cross-section used to drive bolts and screws that have a hexagonal socket in the head. wikipedia Originally named Allen Manufacturing Company, the business produced hexagonal set screws and wrenches to fasten them. The terms Allen wrench and Allen key are derived from the Allen brand name and refer to the generic product category hex keys.