How to use an Allen key
An Allen key (hex key) is the L-shaped tool that comes with most flat-pack furniture. Used the right way round, it gives plenty of grip and turning force; used the wrong way, it rounds out the bolt head.
- Time
- about 10 min
- Difficulty
- Easy
- People
- 1 person
- Steps
- 6
Tools needed
- Allen key of the right size (supplied, or a metric set)
- Optional: a hex bit for a screwdriver handle
Parts to check first
Before you start, lay everything out on a soft surface (the flattened box works) and check it against the parts list in your manual.
- The bolt or screw you are turning
- Its washer, if the manual shows one
Step by step
Step 1: Check the size: the key should slide fully into the hex socket with almost no play. A loose fit will round the socket.
Step 2: Push the key all the way into the socket, not just the tip.
Step 3: For speed while the bolt is loose, hold the long arm and turn the short end in the bolt, spinning it quickly with little force.
Step 4: To tighten, flip the key: put the short end in the bolt and turn the long arm. The longer lever gives much more force.
Step 5: Turn clockwise to tighten and anticlockwise to loosen (unless the manual shows a reverse thread, such as a bike's left pedal).
Step 6: Tighten until the bolt is firm and the parts are pulled together, then stop. Flat-pack fittings need firm, not maximum, force.
Common mistakes
- Using an imperial key in a metric bolt (or the other way round), which fits loosely and strips the socket.
- Only putting the tip of the key in the socket.
- Fully tightening each bolt as you go, before the frame is square.
Safety notes
- If a key slips, your knuckles hit the furniture; keep your hand in line with the turning direction.
- Replace a key with rounded corners; it will damage bolts.
This is general guidance for this type of product. Your product's own manual comes first: follow its order, fittings and torque values where they differ from this page.
Updated 2026-09-30