I've tried this on many different types of doors, and i have yet to see this work. the beveled part of the latch that you need to get the slide into is too far into the door jamb. It's a good idea, but not very effective.

Bit late on this wagon, but thought I should point out, MOST exterior doors open into the building! Some double French doors are hinged to open out, but as noted, they have a strip covering the lock stile gap, blocking access from a slide.

I made something kinda like this out of my old school ID (made just like a credit card). This mostly works on doors inside buildings (like a teachers classroom) or on doors that aren't as important to keep locked. For example, this would never work on the main door to my house as it has 2 dead bolts on it, but it works on doors inside my old school. Long story short, I was showing a friend how to do it. I opened the door, but he was tired of standing and waiting for our teacher to come to unlock the door and he went inside. We both got an office referral and couldn't do any "fun" stuff they plan for us at the end of the year. This was about 2 weeks before the last day of school. There wasn't anything against it in the rules book. I even asked the principal to tell us what rule we broke, and she couldn't :P

Cool i've never seen this before, i have a credit-card shaped 1.5mm thick piece of aluminum which lets me into many rooms at school previously un-accessible to students :D me and my friend went on the roof once :P

Use a thin putty knife... I used to repo houses and I have locked my keys in my own house... yeah it works as long as there is no deadbolt.

Any state in Australia will have the police recognise this devise as an implement and it is an offence to carry such an implement. They will charge you with that offence.

Lots of comments already, but being a licensed locksmith in California, I cant help but chime in. This will work on many doors. If the deadlatch, that second smaller finger on the latch, is functioning this will not work. For the deadlatch to function, the door and strike must be aligned reasonably, but not perfectly. There can be up to 1/8 inch gap and a deadlatch will still do its magic if it is a quality lock, not residential grade or hardware store variety. The latch guard is there to help prevent this type of tool, but a worn or low quality lock will still let you past if you persist. Using a tool other than a key is breaking and entering if you are not documented as someone with authorized access, example your ID with matching address or work ID etc... As someone else mentioned, some states - CA for sure, treat carrying a tool shaped for breaking and entering as a crime unless you can prove at the time you are caught that you are trying to gain access to somewhere you belong. As a student, you are in a gray area breaking into a classroom. You are expected to have reasonable access to your campus, usually a staff member is implied but not always stated in black and white. This is why your principal didnt know what to do with you. Anyway, good instructable. Always proceed with caution whenever you subvert security measures, mechanical or electronic. Keep studying the locks, you may make a great locksmith some day. It is still fun breaking in to things even when you have permission from the locked out owner right there with you. You also get to be the hero of the moment and the pay is good without having to serve time. : ) Houdini was a locksmith in a way, he didnt practice locksmithing but knew more about locks at the time than most locksmiths.

I would be careful before making one of these... many states have laws which categorize tools like this as "burglary tools", which you can be arrested for possession of.

you can use these to rob a house, you probaly can get areted for udeing these

most doors I've encountered in places I would actually care to do this have a second finger that recedes when the door is closed, not allowing the latch to be opened this way

Great Instructable but at my school the looks are just flat so it wont work.

This doesn't usually work on French doors or industrial doors, with or without industrial locks.

did this using a prepaid card when our Computer room was locked. also did this to one of our school doors(which had a slide guard.) this is hard to do if the slope part is on the opposite side (what the school did to the class doors.) Had to use a wire from a Christmas decor to open it by inserting a U-shaped wire the puling it out while pulling the door(knob) hehe. It worked.

nice easy and effective in theory... but if a door is properly mounted it should not have enough gap to get the shim into the gap between latch and catch... better study lock picking too so you have another trick up your sleeve.

I use my school ID card and it works on the non-slide guarded doors

Worthless on a deadbolt.

breaking and entering 101

When I stayed in one of the grad student apartment buildings at Stanford, I discovered that I could open my apartment door in two seconds with an ordinary credit card.

In fact, I discovered that I could open all the doors in th entire, 12-story apartment building with a simple slide of a credit card! 8-/

Nice. The only time I've done it was with a loop of weed-eater string... we had to improvise. Slightly unrelated, the doors to the gym at my school lock with posts that slide into holes in the ground. I discovered that you could open the door and let yourself in by sticking your hand under the door and pushing the pin up. A couple of weeks later they added a guard so your hand wouldn't fit....