Terms of the Trade: What Is an Allen Wrench? Terms of the Trade: What Is an Allen Wrench?
An allen wrench (or hex key, or allen key) is a small tool with a hexoganal-shaped end to work with bolts and screws. Because it can be made so cheaply, you'll usually find an allen wrench with store-bough furniture that requires assembly at home. However, they are available for purchase in sets with varying sizes.