I have a leak in my single handle bathroom faucet. I can't find any stamp or marking on it to indicate the manufacturer. Turning off the hot water fixes the problem short term. I have found some great online tutorials for repairing all potential types of these sinks, but I can't get the handle off to even begin to work on it. We have several Allen wrenches but none fit. It does not appear to be a typical screw, or maybe it is not a screw at all? It looks like a post that is threaded around the outside with a perfectly round hole in the center that is not threaded. The faucet is only five years old and I don't want to replace the whole thing if it can be avoided.

photo of the bolt

The bright spot in the middle is a post that seems to prevent inserting an allen wrench.

  • 1
    Ooh, secure it so the handle can't be removed. Probably a unit intended for commercial installation in public bathrooms. Hence the post and requirement for a special tool. Aug 25, 2015 at 18:17

2 Answers 2


It looks like a tamper-resistant hex screw. There are specific wrenches for these.

hex tamp res enter image description here

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  • Thanks, this looks exactly like what we need. I didn't know these existed.
    – Cortneyk
    Aug 25, 2015 at 12:13
  • Mind boggling that they'd put a security screw in there. However, if you feel brave, you might try putting a fine (small, very pointy, that is) nail set on the tip of the security post and hitting it at an angle to break the post off. The risk is that you'd simply bend the post and make much more trouble for yourself. Aug 25, 2015 at 13:47
  • Exactly the tack I chose when disassembling my McColloch electric saw to Locktite and tighten up the motor stator bolts so the armature would quit dragging. They had two of those Security Torx screws in the set to prevent disassembly and repair. Pthht! Remove the pin and let me in. Aug 25, 2015 at 18:15

Had similar issue and figured out that it was a metric Allen wrench size (probably typical for hansgrohe and other European fittings?).

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