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This gate is locked with 6 locks. What is the purpose of this construction?

enter image description here

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    $\begingroup$ Is there any copyright on the image? I'd quite like to use it the next time that I am explaining this topic. $\endgroup$
    – Daniel S
    May 15, 2023 at 12:43
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    $\begingroup$ Interesting discussion around this here $\endgroup$
    – Techidiot
    May 15, 2023 at 12:48
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    $\begingroup$ If you arrive to find an unlocked state, you can tell which key was used to unlock it, which may give useful info on who is inside. This might be especially useful if the space accommodates very few people - perhaps even only one person, so you could tell if the occupant(s) are cleaning staff, maintenence staff, emergency services, workers, etc $\endgroup$
    – Bohemian
    May 16, 2023 at 4:35
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    $\begingroup$ @DmitryKamenetsky - OH! That flat rectangular bar goes through the round rod. I thought I was just kind of hanging in place with the other lock locked to it. But obviously (now!) that would be useless - neither lock would be doing anything. Thanks for making me take a good look a second time! $\endgroup$
    – davidbak
    May 17, 2023 at 1:30
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    $\begingroup$ I thought this was a joke. I didn't expect this to teach me something so interesting. It's so simple, yet I needed to read the below answers to see it (somehow my sleep deprived brain forgot that a picture is worth a thousand words), and then I find it so wonderful. Thanks for the Q and the answers. $\endgroup$
    – 0xc0de
    May 18, 2023 at 11:20

4 Answers 4

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Securitywise

It allows any of six different keys to open the gate.

One might ask

Is there an advantage to this over having six copies of a key to one padlock.

... and the answer might be

If the six keys also apply to other padlocks deployed separately, then the key management for operating both this gate and the other padlock is simplified.

Thus, for example,

If the gate secures access to a locker room with six lockers, both the communal gate and the individual locker can be managed by a single key.

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  • $\begingroup$ Exactly. ROT13(Gur xrl shapgvbaf yvxr n frphevgl cnff. Rnpu crefba unf gur xrl gung pbeerfcbaqf gb gurve yriry bs frphevgl pyrnenapr.) $\endgroup$ May 15, 2023 at 12:24
  • $\begingroup$ Great answer with good examples. $\endgroup$ May 15, 2023 at 13:07
  • $\begingroup$ See also en.wikipedia.org/wiki/Lock%6f%75%74%E2%80%93tagout, especially the picture at the top of the "Folding ... hasp", shown in use farther down the page at "A ... device applied to a hoist brake". $\endgroup$ May 15, 2023 at 22:11
  • $\begingroup$ @SteveSummit For the sake of clarity, that link describes the opposite case, where ROT13(nyy ybpxf zhfg or bcrarq gb eryrnfr gur pynfc, engure guna nal fvatyr bar bs gurz.) $\endgroup$ May 16, 2023 at 14:10
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As a technician for a telecommunications company I encountered this arrangement of locks at many tower sites, usually out in the boondocks. Each lock is assigned by the tower owner to a different company that needs access to a site. Any one lock allows the gate to be opened. The company provides keys to their technicians. This allows the site owner to change the lock if a given company no longer needs access. Different companies might be a radio station, any of several two way radio companies, tower maintenance company, etc.

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  • $\begingroup$ Thanks for the answer. I am quite pleased that this is actually used in real life. $\endgroup$ May 17, 2023 at 1:29
  • $\begingroup$ Most enlightening answer amongst all. $\endgroup$
    – 0xc0de
    May 18, 2023 at 11:23
  • $\begingroup$ Similar is an arrangement where a chain is secured by padlocks which form links in the chain. If the padlocks are linked in series, any one key holder can gain access, but if they are fixed in parallel then all keyholders must be present. $\endgroup$ May 18, 2023 at 17:30
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If you arrive to find an unlocked state, you can tell which key was used to unlock it, which may give useful info on who is inside. This might be especially useful if the space accommodates very few people - perhaps even only one person, so you could tell if the occupant(s) are cleaning staff, maintenence staff, emergency services, workers, etc

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Not seen one like this before but:

It allows someone with a key to any single padlock to release whatever that locking pin is securing (looks like a gate but I'm not sure).
Depending on which padlock you have a key to, you may need to slide out up to three bars to fully release the locking pin.

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  • $\begingroup$ Also correct answer $\endgroup$ May 15, 2023 at 13:07

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