An Allen wrench, AKA an Allen key or hex key, is a small hand tool used to fasten screws or bolts with a hexagonal socket. Either end usually works, although some sets only have one end.

frequently used in things like IKEA furniture and ready-to-assemble (RTA) cabinets, can be stripped just like any common screw. They're so named because you need an Allen wrench (aka an Allen key ...