An Allen wrench, also known as a hex key, is a small tool used to drive bolts and screws with hexagonal sockets. It typically has a simple L-shape design, which allows for easy handling and leverage. Allen wrenches come in various sizes to fit different hexagonal fasteners, making them versatile for many applications, including furniture assembly and bicycle repairs. These tools are commonly made from steel or other durable materials to withstand torque. Allen wrenches are often included in furniture assembly kits, such as those from IKEA, and are essential for tasks involving hex screws in machinery and electronics.