It happened a couple of times I had items stolen from my home or car because I simply forgot to lock the doors.

Is there a trick to prevent this absent-mindedness?

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    The best life hack might just be to go buy and use better hardware--This is mostly solved lately. My newish car is very mindful of ensuring that it's locked (locks itself), that I didn't leave the keys (it beeps if the keys are still inside instead of locking), etc. There are most likely similar solutions for front doors now. Just wait 5 years and this won't enter your mind any more... – Bill K Oct 3 '19 at 21:27
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    "How to remind myself to lock my doors" I was going to say "get robbed" but... – Beanluc Oct 3 '19 at 23:12
  • Self locking front doors have been around for decades. Unfortunately if you forget your keys on the way out, you're locked out... – colmde Oct 4 '19 at 8:09
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    That's an interesting question. In my case I have the opposite issue, I don't remember if I locked the door/car when I'm absent-minded, but whenever I go back to check they're locked (I'm slightly paranoid). So the sequence of actions are so ingrained in my brain, that I do them on autopilot. Repetition is the correct answer, and trying to pay attention to the task at hand. You need to keep seeing yourself acting in the correct sequence, and then make sure you follow it to the letter, until that sequence is memorized and deviation will no longer be possible even when absent-minded. – bug-a-lot Oct 4 '19 at 8:10
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    I’ve voted to close this question as off topic because is a “Mind Hack” – Tim Oct 4 '19 at 21:31

14 Answers 14


Some answers give various solutions for the house lock but not the car lock.

I have spent so may hours looking for my car keys that I now habitually only ever leave them in one place.

An extension of that would be to have two key hooks. You label one hook "locked" and the other "forgot".

Then when you hang the car key on the hook, the reminder is there. Hopefully, the second hook is never used except as the reminder, or maybe you want to leave the car unlocked for now, to load/unload it, and you'll notice later that the key is on the wrong hook.

In general I have found that a simple reminder notice does not do any good, because I get so used to seeing it that I ignore it after a while. So swap the labels around once a week.

  • I think this one would work for me... thx – Michael Verschaeve Oct 3 '19 at 15:11
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    This seems essentially as easy to become complacent with as notes IMO. It seems like you would very quickly start to just always leave it on the "right" hook without thinking if it should be there or not. – JMac Oct 3 '19 at 17:09

Lock the door immediately after closing it

It sounds pretty simple, but it works (for me).

Whenever you close the door, immediately lock the door as well.

Try to combine this into one action: with one hand you pull the door closed while the other holds the key and locks the door.

You should aim to never do anything between closing the door and locking it.

The shorter time there is and the fewer things you do between when you close the door and when you lock it (on average), the stronger your brain will associate these two things and the easier it will be to remember to lock the door (you might even start automatically doing it after a while).

Even if the door closes by itself (e.g. with a spring), you can still use this strategy by always making sure to manually close the door instead of letting it close by itself.

Pro tip: if you don't need a key to unlock the door of your house from the inside, don't ever put your keys in your pocket or bag while inside. Instead, put it right next (or on top of) to whatever else you always leave the house with (e.g. your wallet or bag). Then you'd pick up your keys when leaving the house and you should physically keep them in your hands while going out the door, which would make it much easier to remember to lock the door.

If you regularly make multiple trips to your car (or similar) and the car is far enough to close the door (but not lock it) or the door closes by itself, this may not work perfectly. But you may still be able to combine it with any "final check" you may do the last time you go through the door. Or split it into multiple trips where you first put everything by the door on the inside, then on the outside (then lock the door), then carry it to your car.

Put your keys away immediately after locking the door

You can use this in combination with the above.

Put your keys on the table (at home) or in your pocket or bag (when going out) immediately after locking the door.

If you're still holding your keys and you didn't just lock the door, you need to go lock the door (or at least check if it's locked).

I quite frequently use this strategy of combining things I want to remember with things I already do.

This would probably work best if you're already very intentional about and conscious of your actions (instead of doing things absent-mindedly). Although, if you aren't, trying to do what's suggested here might help with that, at least a little (because practice makes perfect).

  • This is what I do. Always lock your door. Doesn't matter if your just getting out of the car to pump gas or out of the house to get the mail. Get in the habit of always taking your keys and locking the door and you won't have issues. – pboss3010 Oct 3 '19 at 20:00
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    +1. The OP is not performing the ritual correctly; they're doing something else in between closing the door and locking it, like taking their bag to the car first or something. If so then just leave the door open.... How often do you forget to close the door? Yeah, never. Can't leave the door open because pets? Then put the bag down and lock the door. – Mazura Oct 4 '19 at 0:56
  • Having the keys in your hand is a good way to memorize the ritual. Over the years I have trained myself to automatically check keys, wallet and mobile phone before I am leaving home and I never forget to lock the doors. I just feel wrong if I don't check. – Sulthan Oct 5 '19 at 17:23

Get an "automatic locking door lock" with a number pad. It will automatically lock the door behind you.

Forget your key? No problem: It's a number pad, so no key required.

Source: https://www.amazon.com/Advanced-Security-TurboLock-Keyless-Keypad/dp/B06WW2HHZC/ref=sr_1_16?keywords=automatic+door+lock&qid=1570123735&sr=8-16

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    Simple mechanical locks that automatically lock themselves exist as well. They're the norm in Finland but apparently not in most of the world. I don't quite understand why; I never want my front door to be closed but unlocked. – JollyJoker Oct 3 '19 at 10:27
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    @JollyJoker The simplest reason is that those sorts of locks result in more instances of people having to call a locksmith because they've locked themselves out. The upside of having to lock the door from the outside it makes sure you've got the key with you. – anaximander Oct 3 '19 at 12:45
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    @Mast Installing a door lock is a simple job requiring just a few screws. It can be done in a few minutes from personal experience. – SurpriseDog Oct 3 '19 at 17:28
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    @Benjamin I wasn't aware he meant a lock in the door, thought it was going to be a stand-alone pad next to it. There was no picture yet. – Mast Oct 3 '19 at 18:51
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    There are automated solutions for most things that involve people simply 'forgetting'. Car locks included. As a programmer this always seems so obvious to me that I forget it's not intuitive for most. – aaaaaa Oct 5 '19 at 13:45

Easiest and probably cheapest is put a sticky note at eye level on the door (or on the shoes) saying LOCK THE DOOR.

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    Oddly enough this is probably one of the best methods. Just like they put a sticker near the speedometer of a car telling you to keep left when driving a UK rental. It's simple, but it works. – Mast Oct 3 '19 at 9:09
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    For me, notices like this work for a little while but eventually just become background which is filtered out and ignored. – Mark Booth Oct 3 '19 at 14:04
  • If you drive to work, put a similar sticky note on your car's instrument panel/dashboard. That way you're reminded of it as you drive away. Get a cheap WiFi connected camera so you can check, from the driver's seat, if you actually locked the door. – Eric Seastrand Oct 3 '19 at 18:50
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    Better yet; put a note on the car dashboard saying "did you lock the house door?" for when you're about to leave, and a note on the house door that says "did you lock the car door?" for when you come home. – Bilkokuya Oct 4 '19 at 11:12
  • @MarkBooth while it's quite true that your brain will eventually filter out the note, it should have also developed the habit of performing the action on the note by that time. Especially if you're intentionally paying attention to the note as a reminder. – FreeMan Oct 4 '19 at 15:39

I have a 'leaving the house mantra' of "Keys, Wallet, Phone, Id".

Part of the mantra is to tap the location each of these items to confirm it is there, then I grab my keys so that I have them in my hand, ready to lock the door after me, and unlock the car door. The physical reinforcement helps to solidify the connection between the thought and the action - You don't just know that you have everything you need, you feel it too.

I don't have a similar ritual for leaving my car, as my car keys are always in hand after turning off the engine, but I do always check mentally that I've locked it before walking away, and check physically if I'm not sure.

As houninym suggests, it doesn't take many repetitions to form a habit. Do it every time, even when you don't need to, and soon it should become a self sustaining habit.

  • That's my mantra as well. (I say wallet instead of Id but it's the same thing) – Mayo Oct 4 '19 at 13:01
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    Ah, Wallet and ID are separate for me @Mayo as my work ID doesn't fit in my Wallet. *8') – Mark Booth Oct 4 '19 at 14:14

There's a saying about it taking three repetitions (or 21...) for something to become a habit. A 2009 study seem to indicate it takes about 66 days to become habitual - https://metro.co.uk/2016/12/30/how-long-does-it-take-to-change-a-habit-6351291/. So you need to remember to lock your house and car every time for a couple of months for it to become an ingrained habit.

If that's true for you , there's no point in spending a lot of money to change your house locks... just a post-it note highly visible on the exit door for two months may be enough. The same for the car might be enough. After two months being reminded to lock the door it may become habitual!

It's also something that you may get financially reminded of... most household or car policies won't cover you if you leave the house / car unlocked. So if you walk out the door and find your nice car gone because you didn't lock it, or come home to find the place ransacked because you didn't lock up after yourself (and your car stolen because your car keys were on the table in the unlocked house) you won't find the police or the insurance company very helpful.


set a door alarm I found some door alarm in my country that it can be program schedule at one time if door is open that will be sound. Also, that had a lot of ringing tones. :-)

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    Uh... can you help me understand: the gadget you mentioned will give an alarm when the door is open - that means, when there’s some space between the door and the frame? Or when the door is closed, but not locked, so that anyone could enter the room by pushing the handle or turning the knob (depending on the model)? The former probably wouldn’t help the asker? – Stephie Oct 3 '19 at 5:38

Use a Berlin Key

It is not going to work on a car, but I think it is worth mentioning.

The Berlin key is a key for a type of door lock. It was designed to force people to close and lock their doors, usually a main entrance door or gate leading into a common yard or tenement block.

more on Wikipedia

demo gif

Source video: https://youtu.be/UW4jZLEgaiU

Another video: https://youtu.be/4wE_6e3GPe4

  • Can you please upload the gif through the edit page instead of to Imgur? This will make it hosted directly on Stack Exchange's network and more likely to be viewable. Some corporate firewalls block Imgur. – Captain Man Oct 3 '19 at 18:22
  • @CaptainMan Stack exchange use imgur to host their image. I wont reupload it because of the size "Your image is too large to upload (over 2 MB)". Feel free to edit my post with a new link though. – aloisdg moving to codidact.com Oct 3 '19 at 22:24
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    Wow, while kind of interesting, I definitely wouldn’t feel comfortable if my door was secured by this kind of lock. Picking this is probably a beginners’ exercise... – Stephie Oct 4 '19 at 11:31
  • Now we need to get the LockPickingLawyer to see this! – SurpriseDog Oct 4 '19 at 22:37
  • @Stephie This kind of locks is actually not so easy to pick using common methods used by lockpickers. However, all you need is a set of similar keys. In this case, breaking the door frame would be much easier than trying to pick the lock :) – Sulthan Oct 5 '19 at 17:27

As a supplement to the other answers, one thing I always do it press the lock button twice so the car honks. The audible honk helps me remember that I have done something. This is more for remembering if you did it in public than at home.


You might try to put your keys in the door lock when you get home. And when you are leaving they will be quite close hopefully visible.

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    The door lock is on the outside of the door, so anyone could take the keys. But the keys could be placed on the inside door handle to accomplish the same effect. – BrettFromLA Oct 2 '19 at 18:10
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    @BrettFromLA Believe it or not, there are still many places on this planet where doors are keyed with skeleton keys. These have openings on either side of the door, so you can leave the key in the lock on the inside. See a picture here: pinterest.com/pin/15199717465082988/?lp=true – kmort Oct 3 '19 at 0:22
  • @kmort Thanks for that. I've seen this on interior doors (between rooms in a home or business), but never on a front door. Now I know they exist! – BrettFromLA Oct 3 '19 at 14:04
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    @kmort Leading to the classic trick of slipping a piece of paper under the door and pushing the key through from the other side so it lands on the paper and you can pull it back under the door. There's a reason most (but apparently not all) of the world stopped using these... – Darrel Hoffman Oct 3 '19 at 14:17
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    Where I live there are many locks where you use the key on either outside or inside to lock or unlock but can not push the key out from the other side. (The key on the inside often blocks a key from the outside to be used.) – Willeke Oct 3 '19 at 19:52

When you turn off the engine after parking, don’t actually pull the key from the ignition just yet. Instead, gather whatever you want to take from the driver’s seat and take the key last. Put your finger over (but don’t press yet!) the button to lock. Exit the car with your finger still over that button.

Two options here: either you want to get something from the back seats or boot or you don’t. If not, close the door, lock, and put the key away. If yes, get that but keep the finger on the lock button. Close whatever else you opened, lock and put the key away.

What about if you need to get something that you can’t carry right now? I suggest locking the car anyway. With time, you will generate the automatism that you lock the car whenever you go away from it and unlock it once you get back. 200 ms inconvenience for great benefit.

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    Your mileage may vary on this one. If I don't take the key out of the ignition immediately after I turn my engine off, I invariably forget it in there and have to open the door again to retrieve it. – Demonblack Oct 3 '19 at 15:00
  • My car is one of those "keyless" fob models and doesn't even have a spot where I could insert a key for ignition... – Michael Oct 3 '19 at 16:10

Squawk like a hawk everytime you lock the door. You'll not forget whether you squawked like a hawk.


How can I remember?

That's a mind hack, and not on topic for this site. You can however mitigate the effects of forgetting to lock using technology:

For houses: Fit a self-locking door lock that is unlocked by a code or fingerprint, or keep a key well hidden (not under a plant pot next to the door) in case you become locked out. Upgrades from this level of locking would probably be something like a smart home type intelligent door lock that can be secured remotely using a phone etc - and if you have that you might also have movement sensors inside the house that can lock the doors after a period of no activity

For cars: keep nothing of value in a car, and don't bother locking it. If you do lock it, have a spare key attached to the car somewhere (magnetic boxes exist for this purpose). Consider fitting an aftermarket alarm that will lock your doors for you after a time out. If you're then concerned that this device will lock the car keys in the car, defer to the aforementioned magnetic box idea - it doesn't have to be a sophisticated key with a transponder for starting the engine, deactivating the alarm etc - just a mechanical key that will go in the mechanical lock in the door and open the door will be enough to regain you access to the intelligent key that is locked inside the vehicle


The obvious answer is habit. Need to build a routine that involves locking the respective doors. For the car, perhaps using your backseat to place your duffle bag that usually goes with you. Grab the bag then lock the door using the fob. Always anticipate the beeping as the last step before you walk away. The house might need a keypad lock. Similar idea though. Last step before walking away from the door in or out should be wanting to hear the lock engage. Note: if you're married, you probably already have developed the habit of putting the toilet seat down! So there is hope!

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