I have a storage room in my apartment block (each apartment in the building has a private storage room in the basement). I suspect that someone may have entered there, maybe the landlord who lives in the same block, or another person who may have lived here before and could have kept one of the copies of the key.

I was thinking about changing the key, but I'm wondering if I can come up with an idea that would be cheaper and also could tell me if someone has entered.

A security camera would be great, but there are no power outlets (the electricity bill of the storage rooms is shared by all neighbours in the block, so they don't want people to plug certain electric devices there "for free" and there is only a light bulb with a switch). I could use a power bank like the ones used for smartphones but I guess it would only last a few hours. Also, the camera could not send the images anywhere from there.

I also thought of putting some object behind the door that would break when the door is open but I would also break it when I enter

Do you know if there is any clever idea for this or some device that I can buy?

  • 12
    There are all sorts of "spy tricks" for this, that are probably off-topic, like a hair across where the door opens. There's a discussion at lifehacks.se for those. That also discusses some more on-topic ideas like battery-powered alarms
    – Chris H
    Jan 26, 2022 at 11:28
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    There are motion-activated cameras which can last for months on a single charge, recording 10-20 mins per day to an internal SD card - google "wyze cam outdoor" for an example.
    – brhans
    Jan 26, 2022 at 11:32
  • 3
    Have you never seen a James Bond film? Pull a hair from your head and catch it in the door frame as you close the door. Look for the hair to be there when you return. If it's not, somebody has opened your door. Either that or someone saw you put it there and is messing with you...
    – FreeMan
    Jan 26, 2022 at 12:47
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    @Freeman - when I tried that trick using the dog hair, there were additional hairs when I returned. I concluded that many more people had not entered the room.
    – Willk
    Jan 26, 2022 at 15:45
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    I’m voting to close this question because it's off-topic, asking for either hardware recommendations or life hacks. It would be a duplicate of one at lifehacks.se anyway
    – Chris H
    Jan 27, 2022 at 9:40

7 Answers 7


What country are you in? If you are in North America and the light switch is inside your locked space and there is a normal E26 light bulb socket, you can BUY an adapter that will allow you to take power from the light socket and still switch the light on and off by pulling a chain.

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If there is wifi down there, in any country you can buy a combo light/camera where you would leave the light switch in the On position and control the camera and light from your phone.

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Without electricity you could rig up a Polaroid flash camera to take a picture when the door opens, by connecting the door to the shutter button with string and pulleys. The tresspasser could of course steal the photo and/or the entire camera but at least then you will have confirmation of the event. Or you could put the camera in a securely mounted steel box but that seems like getting too far ahead of things.

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I think it was mentioned in the comments: Non-wifi security cameras that are motion/light activated and record to a memory stick can last for weeks or months and can be hidden easily and cleverly. The come in the form of picture frames, external hard drives, toys, etc.

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  • Spain. Both are great answers but I can't vote up! Jan 26, 2022 at 13:53
  • Pretty much applicable in Europe.
    – fraxinus
    Jan 27, 2022 at 16:29
  • @fraxinus is there anything like that first device in any European country? To take power from a light socket using a device sold legally in stores?
    – jay613
    Jan 27, 2022 at 16:55
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    Legal, no. I doubt it is legal in North America either. But in regard to available, pretty much yes - I used to own one. Rather safe if you know what you are doing - i.e. if you plug only low power, double-insulated appliances.
    – fraxinus
    Jan 27, 2022 at 17:39
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    "steal the photo and/or the entire camera", well along those lines: just leave a valuable in plain site. When it's gone...
    – P2000
    Jan 27, 2022 at 17:49

Search for "trail camera" in aliexpress, Amazon, or any other retailer.

These cameras are meant to be left in the forest to take videos of animals. They are activated by a low power motion sensor, so you'll get long battery life (maybe several months).

Of course you'll have to hide it. You can get more inconspicuous models by searching for "hidden camera motion detector", the fake smoke detector is a common disguise for these.

  • 9
    I'd upvote this if it wasn't recommending AliExpress. Trail cameras are also sometimes called "safari cameras". Jan 26, 2022 at 19:43
  • Another keyword to search for would be "game camera" Jan 26, 2022 at 22:08
  • 3
    ...not that a smoke detector would be conspicuous on the side of a tree...
    – gnicko
    Jan 26, 2022 at 22:36
  • wildlife cam ...
    – jsotola
    Jan 26, 2022 at 23:39

Balance an open bucket of yellow paint on a small platform above the door on the inside. Attach the bucket to the door with a piece of string. The string should be long enough that the door can be opened about 10cm without tipping the paint. In the middle of the string put a detachable link or a carabiner so you can reach in and disconnect it before opening the door. The tresspasser will be the one with yellow hair.

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  • 4
    This is becoming a very popular, if somewhat humorously impractical answer... OTOH, this is basically what they do with cash when transporting it so the thieves can be easily caught...
    – FreeMan
    Jan 26, 2022 at 18:24
  • 6
    ..and if that doesn't stop them an anvil or a crate of dynamite would be suitable upgrades. Acme brand of course.
    – Chris H
    Jan 27, 2022 at 9:38
  • 2
    @ChrisH BEEP! BEEP!
    – JACK
    Jan 27, 2022 at 13:21
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    Depends how often people are going in there. If they don't go in there for a month, the paint will already be dried solid. Although of course then the trespasser will be the one shouting "What ***ing ****er put that ****ing bucket on top of the ***ing door?!" which is probably a bit of a giveaway.
    – Graham
    Jan 27, 2022 at 15:12
  • 2
    To the extent anyone is seriously considering implementation details 1) lethal solutions are probably illegal in Spain, and probably excessive to protect empty cardboard boxes, Christmas decorations and extra chairs, 2) To help with the drying-out issue, use a loose-fitting lid with thinned paint or dye or ink.
    – jay613
    Jan 27, 2022 at 15:34

Wedge a dime or some small, thin object between the door and jamb and lightly mark the door where the object is. If the door is opened, the object will fall and if the person notices it and tries to puts it back, they won't get the height right.

  • 2
    ...except for a helpful marker on the door frame that you left showing where to put the object ?
    – AutoBaker
    Jan 27, 2022 at 14:04
  • 2
    @5Diraptor "lightly mark the door", a pencil point, an indentation, etc. Not suggesting outlining the object with a magic marker.... :-)
    – JACK
    Jan 27, 2022 at 14:12
  • 4
    @5Diraptor That's why you mark the door frame, but put the object an inch away - if it ends up at the mark you know it was replaced by someone else.
    – Travis
    Jan 27, 2022 at 18:37

If the door opens inwards, then place a marble behind the door when you are closing it, with only an inch or so to go before fully closed. If someone opens the door it will roll the marble away and they likely will not even notice it. To check, you open the door only an inch and feel behind the door to see if it is still there before you enter


It depends on the doorframe if you can find a good solution to this.

The best way ( from own experience ) is to put something thin and light in between the doorframe and door. this would work with doorframes that fall over the door slightly, but also if the door is level with the doorframe

piece of paper falling when door is opened, scene from: death note

you can use anything, a toothpick,piece of string, leaf, paper, or something else thin enough to go between the doorframe and the door.

You can place it on the handle side, or on the hinge side. This way you can tell it was opened before you actually open the door yourself. Or even put two of them in there on both sides of the door ( hinge side first, then handle side). Make a note or photo of the exact position they're in.

This would only give an indication that the door was opened, not who or what opened it. ( and yes the photo is a scene from death note )

  • This was already addressed in this answer and a lot of comments. Care to add anything new? If you'll take the tour, you'll note we're a bit different than other sites and simply repeating other answers isn't really all that helpful.
    – FreeMan
    Jan 27, 2022 at 15:42

I suspect that someone may have entered there

How did you arrive at this theory?

Apparently, you've already detected unauthorized access. What good will it do to just detect the activity again?

It sounds more important to identify a perpetrator at this point.

I think you should open a conversation with the landlord along the lines of:


I was wondering, is it possible to change the lock on my storage unit?

I went in there the other day and things seems to have been moved around.

Now, your follow-up action should be based on the landlord's response.

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