Why Do We Call It an “Allen Wrench”?

Furniture giant IKEA has a not-so-secret weapon at its disposal, and it’s not the Swedish meatballs. Inside virtually every ready-to-assemble product requiring screws is a complementary Allen wrench, a compact hexagonal tool that can quickly twist and secure fasteners for bookshelves, tables, and other home goods. It’s a tool so necessary the company—and plenty of others—consider it as standard as the assembly instructions.

But is there an Allen behind the Allen wrench? Is its etymological history as fascinating and convoluted as that of the Crescent wrench or monkey wrench?

1. A Wrenching Portrayal
2. Allen vs. Hex Wrench
3. IKEA In the Toolbox

A Wrenching Portrayal

Most people have encountered an Allen wrench (or Allen key). It’s the L- or S-shaped tool with a six-sided head that can easily be gripped between your thumb and forefinger to assemble everything from furniture to exercise equipment that ships “flat” or unassembled, which saves on shipping costs. Have a look:

The Allen fits snugly into the recess of the screw or bolt being used, which is also six-sided. The tool is, therefore, commonly known as a hex wrench or hex key.

So how did Allen enter into it? Like most non-proprietary consumer products, it was an attempt at branding.

In 1910, William G. Allen, owner of Allen Screw Manufacturing Company, began marketing hex wrenches, which had already existed in some form or another since the 19th century. They were intended to compete with similar square wrenches, which reduced tool slippage. (Think of how a flat-head screwdriver slips completely off a screw, a potential hazard rectified by recessed screw heads.) The wrenches were meant to be used with a screw that had a hexagonal recess, which Allen had filed a patent for in 1909; he called it the “Allen Safety Screw.”

If hex wrenches existed before Allen, why did they become his namesake? Simple—Allen publicized them, stressing how much better it was to have a tool that took more of a lock-and-key approach to joining with the screw.

The timing was fortuitous: Industrial manufacturing was beginning to take off, and the need for tool designs that lessened risk for factory workers was rapidly rising. Allen wrenches and accompanying screws were quick, efficient, and reduced slippage. Best of all, the diminutive tool cost only pennies to make—a big reason it’s so pervasive.

Of course, not everyone tried to pass those savings on to consumers. In 1983, General Dynamics drew the ire of government officials when it attempted to bill the Pentagon $9609 for the wrench.

Allen vs. Hex Wrench

Is there any material difference between an Allen wrench and a hex wrench? Not really, though you may not find the tool under the name Allen in non-English speaking countries, where it’s still referred to as the hex wrench or key.

Nor has the Allen wrench changed all that much. Sometimes, you may come across an Allen with a rounded tip that permits more flexible turning in hard-to-reach areas; John Bondhus created the ballpoint, which he dubbed the Balldriver, in 1964.

The IKEA Allen wrench is also a bit different, with two heads on opposite sides of the wrench to accommodate different fastener sizes. Speaking of IKEA ...

IKEA In the Toolbox

According to IKEA, the company began incorporating Allen wrenches and screws into its assortment in the 1960s. The tool represented a larger idea: The ability for a consumer to bring an unassembled product into their home and have it ready that same day rather than rely on outside labor or expensive delivery of a fully assembled item. Nor did they need an expansive toolbox—the Allen wrench could tackle the job by itself.

IKEA acknowledged not everyone would find the task pleasant. “We do half—you do half,” read the ad copy. “We make furniture and send it out in flat packs. You groan a little and put it together!”

In a 2011 New Yorker article on IKEA, author Lauren Collins referenced the so-called “IKEA effect,” where such toil can make a hunk of particle board feel more valued and earned. Collins also wrote of the wrench: “The Allen wrench is the egg to IKEA’s instant cake mix.”

IKEA values the tool so much that in 2021, the company commissioned an art project consisting of an illuminated wrench—a tribute to the tool that’s made so many college dorms, apartments, and living rooms feel more like home.

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