I have a number of bikes. I have found a certain type of bike lock to be optimal. Thus, I have no less than four keys of similar type. The lock manufacturing company changed the design of the key at some point of time, so two of the old keys have an identical base and two of the new keys have an identical base.

When needing to lock or unlock a given bike, I can distinguish between the old and new key base type, so that leaves me two keys to choose from. If I blindly use a key, 50% of the time I guess incorrectly.

Is there some way I can easily and durably mark the keys so that I can distinguish them from each other?

  • Possible duplicate: lifehacks.stackexchange.com/q/9614 And also interesting: lifehacks.stackexchange.com/q/11807
    – Stephie
    Commented Sep 6, 2021 at 19:29
  • I last had this problem when I bought 4 identical bike locks. A 2mm drill bit solved the problem - between 0 and 3 indentations drilled in every lock and key body, so now I just look at the lock, count the indents and find the key with the same number of indents
    – Caius Jard
    Commented Oct 1, 2021 at 23:05

1 Answer 1


My solution is to mark they key shafts by a small number of rubber O-rings that are slightly smaller than the key shaft diameter. By buying a collection of O-rings of varying sizes, one can get enough of these small O-rings to mark a huge number of keys.

This works as long as the number of O-rings to put on the key shaft is reasonable and the key type has a slightly longer shaft than it strictly speaking would need.

The idea is that if one has N keys that are otherwise identical to each other, one marks them by putting:

  • Zero O-rings on the first key
  • One O-ring on the second key
  • ...
  • N-1 O-rings on the last key

If the O-ring is smaller than the key shaft, it stays on the shaft by being stretched and it's not easy to accidentally remove it. At least on disc detainer lock keys, the cuttings on the key act as a retainer, so if one accidentally pushes the O-ring outwards from the root of the shaft (very unlikely), the cuttings catch the O-ring and make it practically impossible to accidentally completely remove the O-ring.

  • Hi Juhist, Welcome to Lifehacker. We hope you enjoy sharing knowledge and creativity. What happens when the number of O-rings prevent the key from being fully inserted, after 2, say? Plan B might be to also alter the key-order on the key ring.
    – Stan
    Commented Sep 6, 2021 at 17:45
  • Could you add a photo as an example?
    – Pablo A
    Commented Nov 11, 2022 at 18:52
  • The problem of posting photos of keys is that it's possible to decode information from the picture, and subsequently construct an identical key. It's like posting a picture of your password! hackaday.com/2015/09/18/…
    – juhist
    Commented Nov 12, 2022 at 8:08

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