I will be on leave so as a precaution I want to see if somebody has entered my room with the door being locked from outside.
I've seen some people close little slips of paper in the doorframe (hinge and/or handle sides) that would fall when the door is opened, and/or stack boxes against the outside of the door in what appears to be somewhat random fashion but where the edges and corners line up with pen or other markings in a particular way, and compare before vs. after pictures.
Edit: The above is the low-tech solution. Logging door sensors and/or a motion activated camera are higher-tech solutions that should not be overlooked by someone who arrives at this question/answer looking for similar ideas.
In Dr. No James Bond placed a hair across his door closures which would fall off as soon as somebody opened it.
Of course you have to test if the hair will stay stuck for the time you are on leave. Consider using some glue.
Install door sensors. These work similar to the ones on a garage door, but you can buy them for interior man-doors. Some of them are very inconspicuous.
Wire it up to a Raspberry Pi or another device that can record when the door was opened and save it to a log. There may even be ready-made products that do all of this, but my inner geek would want to wire it up and program it myself.
When you return, simply check the log and make sure there are no unexplained log entries (i.e. nothing between when you left and when you returned).
If you cannot trust your roommates, a better option might be to move.
As you're shutting the door, get it as closed as you can while still reaching your arm in, and set something on the floor (solo/dixie cup, nut, anything that will move easily when pushed by the door) right by the door.
When you come back and open the door, check to see if you're pushing it or if it's already been shoved from where you placed it.
Stick gum on several spots like light switch, door knob, drawer etc., whereever you think the intruder might touch.
Take a picture of the gum. When you return, if there is a finger print or if the gum is in different shape to that of your picture then someone has touched it. You know what that means, then, don't you?
With my approach, you not only can say if someone has broken in but you also MAY have their finger prints. If they manage to remove the gum to protect their identity, you at least would have managed to gross them out. haha
As many people have seen Death note animation series so I am just taking about that scenario where he comes to know that someone has break his room and tried to come in. In chapter 16 of Death note manga there is situation when Ryuzaki comes to know that someone has tried to enter his room. But the fun part is how he did that .
It's great if you will read those images which I have attached to this answer it will help you for better understanding.
If you hate reading it try seeing this video:
Here is the link of death note series Episode 8 and if you will start seeing it from 10:00 then you will see the whole explanation about how he comes to know that someone has tried to come in his room.
At first he sets one little paper trap on his door which he used as decoy.
The second trap was that the handle of his door. He purposely lowers the handle of the door by 5 millimeter while he goes out of his room but most of them don't notice this so if someone may have break his room then he will notice that the handle will go straight horizontally.
The third one is the pencil lead which he used to attach with metal hinges of the door.Whenever he used to close the door he put one piece of lead above the hinges and when someone tries to open the door the leads gets crushed but he usually pull the lead out before he open the door but then if someone will try to open it then it will break easily.
3 levels of security which anyone can apply.
You don't need anything which is too costly because the things which were used in this scenario is really common.
You can implement your own ideas on this whole plan by putting anything else.
Never ending, you can use this again and again without any waste of money (except that pencil lead)
Many people see that paper trap because its quite common now days and they get happy that they have identified that trap and then they try to put it back if they are trying to go into your room but most of them don't even think that there can be even second trap and they neglect that part which increase the chances that your plan will work and even if someone will come to know about the second trap which is quite rare or if by the way the second trap fail to work according to plan then you will have one last trap there which will not fail.
- The success rate for this scenario is quite high but still there are chances that if someone may know all these tricks.
Images taken from Death note manga series:
Chaper 16: Page 14
Chaper 16: Page 15
Chaper 16: Page 16
URL for these images are :
It's a variation on the existing answers, but perhaps a worthwhile one.
Attach a short piece of string to the top of the door frame, towards the handle side (as opposed to the hinge side). It should be short enough that it's likely to go unnoticed, and it should ideally be the same color as the door.
When you close the door, place the string so it goes over the top of the door into your room.
If someone opens the door, the string will hang straight down, and when they close the door, it will be pushed to where it's visible from the outside. When you return, before opening the door, check if the string is sticking out. If it is, someone has been in the room.
Spread flour (or talcum powder) across the floor - especially in front of the door (and under the windows if you are worried about that).
The state of the flour upon return will be:
- Undisturbed - nothing happened.
- Disturbed - if there are foot prints in it, well, someone stepped in it.
- Cleaned - someone came in, disturbed the flour, and then noticed that it was there and cleaned it up.
My first answer would have been to tamper-proof the door as well, but I like this one too:
Fill up a large bowl with an assortment of candy and leave it in your room. While the contents of the bowl look random and uncounted, you have, in fact, counted it's contents. To enhance the plot, share the candy with your roommates before you leave. Let them know that there is a huge bowl of candy in your possession.
And in the spirit of Jimmy Hoffa's answer, poison the candy.
From ubuntu forums
NE Key November 19th, 2008, 03:51 PM As you leave and close the door place a matchstick or similar inconspicuous object in between the outside of the door and the door frame on the hinge side. When the door is opened it will fall out. You will be able to check, before you open the door yourself, if the door has been opened while you were away.
Besides obvious answers about Books, paper, hairs and stuff like using half of a toothpick...
Have you considered getting a simple alarm system instead of relying on cheap tricks?
I use SimpiSafe at home. Granted at $259 for The 7 piece start package, it's going to be more expensive than hair, a tooth pick or a bag of flour... At the end of it you'll have an actual alarm system:
- No yearly agreement
- $15-25 a month depending on options chosen
- No reliance on local internet - alerts happen via cell phone network
- Read: Works with loss of internet
- Battery powered parts - including battery backup in the base unit.
- Read: Works with loss of power
- Alerts on any status change
- Read: Someone trips the motion sensor? Turns off the alarm system? Opens a window?
- Change different sensors to silently alert
- Change different sensors to alert local authorities (or, in this case, most likely not)
- Useful when you leave for work - not just when you are on vacation/leave
- Applied via small screws/tape. no need for complicated installs.
- Adjustable - get enough for one room... or expand to a household
If you don't like SimpliSafe, other options exist - all with their own pros and cons...
The main point to consider is a REAL alarm system - even if for a single room. Just because you trust your roommates, don't mean that you trust their friends/family. Wanting to protect your stuff while your gone is reasonable. Expand that to protecting yourself daily and find a reasonable option - not parlor tricks.
Draw the blinds so the room is dark, and wire up some kind of energy usage meter to the lighting circuit.