An Allen wrench, also called a hex key or hex wrench, is a small, L-shaped tool used to fit screws with hexagonal recesses, which are often used in small spaces where standard screws are too large or awkward.
Uses - Screws compatible with Allen wrenches are often used in automobiles, motorcycles and bicycles because of their ability to operate in tight spaces.
Sizes - Allen wrenches usually come in a set of different sizes. The most commonly used standard sizes, as established by SAE International, are 5/32, 3/16 and 1/4 inches in standard measure. In metric, 4, 5 and 6 mm wrenches are the most commonly used.
History - The Allen wrench was developed in the early 20th century by the Standard Press Steel Company. The trademark for the L-shaped design was established by the Allen Manufacturing Company in 1943, hence the name Allen wrench.
Complaints - The most common problem using Allen wrenches is misplacing or losing wrenches in the set. They are small and can be easily mixed in among other tools. It is a good idea to keep Allen wrenches on a key ring or in a separate container.
Special Allen Wrenches - Most Allen wrenches, due to their L-shaped design, have a tough surface for your hand when providing torque. Specially made Allen wrenches come with large handles for easier grip. Allen wrenches are also made in a multitool, Swiss Army knife-like contraption for better grip.