My apartment door unlocked itself.....a wood kind of one with a round door handle that key goes into. I shook it when I was leaving to make sure it was locked then I came home to find it unlocked....twice. Does anyone please have an explanation for how this could have happened?

  • 30
    Call your landlord (assuming "apartment" = rental) and request an immediate lock change. If you own the place, call a locksmith yourself. Don't delay.
    – Ecnerwal
    Apr 29, 2021 at 14:17
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    If you can get someone to "house-sit", you can simply remove the lock-set from the door, and drive it to a reputable locksmith's retail location, and they will re-key it for under $30. The actual work is cheap; the big cost of a locksmith is bringing the truck to your location. Apr 29, 2021 at 16:47
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    I would setup a camera to see if anyone is entering and who. If the landlord/maintenance is the one doing it, having it rekeyed won't change anything as they still have the key. Ideally they should notify you before entering, but in cases where someone below you has water coming in from above, they won't always wait for permission if it's a big enough emergency.
    – rtaft
    Apr 29, 2021 at 17:08
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    "How do you find a reliable locksmith" Not Google. Grab a 10-year old telephone book (so you know they've been in business 10 years)... and say you want to bring in lockset to be re-keyed. If they balk at giving their street address, don't be offended - it just means they do outcall only i.e. they work out of their truck and their "home base" is their house. If they ask for your street address then yeah - be offended! They don't need it! Apr 29, 2021 at 17:13
  • 11
    Also make sure you install a CO detector in your apartment.
    – isanae
    Apr 30, 2021 at 10:17

5 Answers 5


Either your door lock is defective, or someone is unlocking the door while you are gone (someone with the key, like your landlord, or someone is picking it open).

  • 16
    To follow up, there are some things you can do to tell if the door was actually opened or not. Cameras and sensors are available for this, of course. Low tech solutions would be something like placing a very thing string between the door and the frame when you shut the door. Test this out first. If the string moves or is dropped on the floor, it indicates someone has opened the door. Of course you would want to place this away from the lock as to not make it easy to spot when someone unlocks the door. Apr 29, 2021 at 14:06
  • 1
    What do you think the chances of the lock being defective are? It is an old door with old lock (key goes into ball shaped door handle)....I did lock and then shake it before I left though (OCD)
    – Kate
    Apr 29, 2021 at 19:45
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    It is possible for the installation to be defective. The latch on our front door will sometimes not "catch" on the strike plate in certain weather conditions. The deadbolt works fine so it's not an issue. If you don't have one, consider getting a quality deadbolt as well.
    – JS.
    Apr 29, 2021 at 22:48
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    @JS The description of this one is that the door is shut and locked when they leave. Then it is unlocked when they return. It seem unlikely that a lock is defective in that way. Apr 30, 2021 at 13:25
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    I once lived in an apartment and came home to find a weird stain on my chair. I got a weird feeling, picked up the phone and hit redial. Someone answered and I asked who it was and he said "Jeff". I didn't know anyone named "Jeff". It was really creepy. Get your locks changed.
    – JimmyJames
    Apr 30, 2021 at 15:47

Most likely, someone is entering your home without your permission. That is probably a violation of your local tenant-landlord laws, but there are other actors who may not know about or respect those laws.

There are several ways this can happen. Some sites have really, really, really bad security. This very long video covers most of them in its first 20% or so. (the rest is about door sensors, card keys and other non-applicable stuff).

Previous tenant

Often they don't change the lock after a previous tenant leaves. Sometimes the tenant is shifty, or sometimes they give a copy of the key to someone else who may not realize that tenant has moved on, such as a friend or contractor.

Master keys

In all apartments, it is normal and legal for the landlord to hold a copy of your key. That is so they can do non-destructive entry when necessary.

It's possible to build a lock tumbler set so that two different key cuts (bittings) will both work. So your lock works with key bitting A and B... your neighbor A and C, your next neighbor A and D, etc. You are issued key B. Your neighbor is issued key C, next neighbor key D, etc. The landlord holds onto key A, which opens every apartment, as well as utility closets, roof access etc.

But of course the landlord doesn't do all their own work; that's not even legally allowed (workers must be licensed). They hire out to contractors. The contractors need access, so as a simple expedient, they hand the contractor an "A" key. At this point, the contractor (on purpose or by mistake) could enter an apartment. Legally the landlord is supposed to give you advance notice of such an entry unless it is an emergency... but that's not the contractor's responsibility, they're there to "Git-r-Dun" and get paid. In an emergency they are supposed to notify you that they had in fact entered - however they may stick that on the outside of the door and other tenants or the wind may tear it off.

If a "master key" gets compromised, i.e. if a contractor copies it, security for the site is blown. Now the landlord has the ignominious task of having a locksmith create a new "AA" key bitting, and re-key your door so it works with "AA" and "B", your next door neighbor's to work with "AA" and "C", etc. for every door on the premises. The landlord often won't bother, or won't even know the key is compromised.

You need to report the entries to the landlord, for this reason alone.

Lock Boxes

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Because nothing says "peace of mind" like a Chinese lock box clamped to a fence, with your house keys inside.

Lock boxes are lockable boxes with a shackle, typically locked to doorknobs or fences, sometimes bolted to the side of the building. They have a compartment specifically for house keys. Whoever can access the "lock box" has the keys inside.

They're intended for everything from Realtors to Fire Department access to dog walkers for Pete's sake.

Some commercial sites infamously have a whole row of these things, one per contractor or service provider. Who knows what keys are in it? These have exploded in popularity in recent years. It is the classic example of the war between "usability" and "security".

This combines badly with the above, e.g. if the management company is dumb enough to put a master key in one, or if the previous tenant put your key in a lock box for a service they once used, and that lock box is latched to a fence, forgotten and waiting for someone to pick it.

Door "dead latches" and strikes

See 6:50 in that video.

You notice the door's latch is just a ramp on a spring. Nothing keeps someone from dragging something (hook, credit card) across the slot and the ramp will make it retract. UNLESS...

Better door knobs have a feature called a "dead latch". It's a typically half-moon shaped "rod" right next to the latch. If it is pushed in, the latch will not retract! It can only be operated by the knob/key. If your door set doesn't have a "dead latch", it needs one.

However, the dead latch has to operate against something in the door frame. That is called the "strike". If the strike is the wrong shape, or misaligned, the dead latch will fall into the hole in the strike, and it won't do its job.

Other jamb problems could even cause the door to hop off the jamb with the wind, and open, and re-close. If the lock automatically unlocks in that case, it could be the wind!

Talk to your landlord.

Anyway, talk to the landlord about your door concerns. Most landlords have no issue whatsoever with you installing premium door knobs (they are pretty standard and don't involve modification) as long as you pay for it and they get a copy of the key. If warranted, you could even use a premium access-control key such as Schlage Primus or Medeco M3... they can't duplicate it and you'd only give them one, so they won't risk leaving it in a "lock box".

  • 2
    In some EU countries, it's perfectly normal and legal for the tenant to replace the lock cylinder with one of their own, without ever giving a key to the landlord (you just store the original cylinder and put it back when moving out). It's illegal for the landlord to enter the property without prior arrangement with the tenant anyway, and in major emergencies (fire), the emergency responders will just break in by force, no time to search for keys. (Newer apartment buildings might have automatic remote unlocking of all doors when the fire suppression system activates.)
    – TooTea
    Apr 30, 2021 at 7:38
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    "Because nothing says "peace of mind" like a Chinese lock box clamped to a fence, with your house keys inside." It's actually kind of nice, if I ever lose my keys (say at night while out without my phone) I can at least get inside using the master key for the apartment building from the lockbox at the entry for which I know the code because a contractor put it on a sticky note on the lockbox once. :D
    – Nobody
    Apr 30, 2021 at 8:45
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    To expand a bit on the subject of deadbolts: the kind of lock you describe (keyhole in the knob) is cheap and very poor. It can be opened with a credit card or any piece of stiff plastic that fits between the door and the jamb. A deadbolt prevents this. In some jurisdictions (mine, in the US), deadbolts are required on apartment doors. In addition, cheap locks are manufactured in a small number of patterns to keep costs down, and it is possible that someone is opening your door by mistake with his key. See holdersecurity.com/2016/05/18/…
    – Wastrel
    Apr 30, 2021 at 14:14
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    LPL videos show how easy it is to open those boxes without knowing the code.
    – JDługosz
    Apr 30, 2021 at 14:51
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    re LPL lockboxes, it really is that easy. i don't have any prior lock picking experience and after watching a few LPL videos I am able to open lockboxes and a few other tricks. practiced on two occasions for about an hour each. tools are cheap 10 - 25 USD.
    – zamnuts
    May 1, 2021 at 23:10

If this has happened more than once, motion sensing game cameras are cheap these days and the comment recommending you put up a camera deserves to be an answer. If someone has entered your place and nothing was stolen, especially repetitively, it might greatly benefit you to know who as it could be inappropriate activity by a landlord or something less OK than that. I'd put up a camera and at most re-key the existing lock so a change is not obvious and you have a good chance of getting video of whatever person attempting to enter one last time.

I had my front door crowbarred open about 10 years ago. Still no idea what if anything they took. Thousands of dollars in recent electronics that could have been hauled out rapidly. Initially my roommate thought a box of loose change had been stolen, but I found it a few years ago after he passed away.

  • While this is a good idea, it remains secondary to securing the access door. Cameras stop nothing, they simply add extra information after the fact.
    – Criggie
    Apr 30, 2021 at 9:49
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    @Criggie If the problem is someone repeatedly breaking into a home for sinister purposes, a new lock won't guarantee long-term safety; they'll probably just switch tactics. A camera might get them arrested. Apr 30, 2021 at 11:14
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    Just as an FYI, make sure the camera streams off-site. My neighbor's house got robbed and the thief also made sure to remove the SD card from their security camera.
    – Machavity
    Apr 30, 2021 at 16:20
  • @user3153372 lets go with "why not both" as an acceptable set of actions for OP.
    – Criggie
    Apr 30, 2021 at 23:28
  • 1
    Yeah the intent of that part is to emphasize the benefit of not changing the look of the lock. Re keying would be easiest, but if it's a recent lock you can probably buy a new set for roughly the same cost or less. Setting up a camera with a net link requires tech skills so a layperson could take some time to get the camera up or be stuck with a monthly fee. I'd go out and buy a game camera the same day and hide it. Especially if the lock is changed and you can put the camera inside, this is likely to be adequate. That said if you have the budget or skill, network cameras are cheap.
    – K H
    Apr 30, 2021 at 23:43

It means someone is breaking into your apartment

It's most likely a handy-man or contractor with some bad intentions. Just google "handy man breaking into apartment". In many cases apartment complexes hire people without a background check.

Immediately call your landlord

Tell them you know your door is locked, but you've come home to an unlocked door twice. Hopefully it's an oversight and the person was supposed to be there. If there were no work orders rekey immediately!

Buy a security camera that can stream to your phone

By a camera that will live stream the apartment and save it offsite. You can set it to alarm when it detects movement. If it is a handy-man, you may have just tipped them off, and they'll be more careful to lock-up behind them.

If it is someone on payroll, the security camera will let you catch them red-handed.

Maybe sleep somewhere else until the new lock is installed

Consider staying at a friend's place. The worst case scenario is a very bad person has you in his sights.

  • 1
    As far as sleeping, simply setting a piece of furniture in front of the door will assure an entry won't be quiet. May 1, 2021 at 22:20

I'm sorry to have to ask this, but starting around my own age it becomes relevant: Is there any chance that, despite your confidence, you really did forget to lock the door/shake the handle on the way out?

As locksmiths and landlords will tell you, one of the early signs that memory isn't as good as it once was is that we start noticing things aren't the way we thought we left them, and it's very common for folks to look for someone to blame it on rather than accept that age is catching up with them. "Senior paranoia" is the extreme version of this, but occasionally forgetting a task happens to all of us and it's easy to misremember when it's a task you do almost automatically and can't imagine not doing.

Heck, even a locksmith occasionally leaves his door unlocked by mistake... Or, more embarrassingly, locks himself out with not just the key but the tools on the wrong side of the door. (My solution to that last: a friend has a copy of my key, so I go borrow that. Best lockpick in the world is a copy of the right key. Even if it does give them a chance to laugh at me.)

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