Ever stumbled back to a hotel room only to realize your roommates have already gone to bed and locked the chain lock on the door? When no amount of knocking can get you in you can release that chain lock with a piece of string or floss.

You need about three feet of string for this to work. Start by looping one end of the string and then open the door as much as you can. Loop the string around the chain with your fingers. Pull the other end of the string over the top of the door frame, and unlock the door. You can also use the previously mentioned rubber band method or if it's a barlock you can use an envelope. As always, this isn't about breaking into someone else's room, but a good way to get into your own when you're locked out. Hit up Secrets from the Yumiverse for a handy infographic walking you through each method.

How to Open a Door Chain Lock or Bar Latch from the Outside | Secrets from the Yumiverse

We've all locked ourselves out of our home at least once or twice, but locking yourself out without a way to get back in—like a phone or a roommate—can be pretty stressful. This snap-apart card fits in your wallet and turns into a full lockpicking kit in seconds.

We've talked about how to pick a lock before, and even given it a shot ourselves on video (with great results). It's a great way to get yourself out of a bind, or just gain a little understanding on your security (not to mention impress your friends). But in a real emergency, you probably don't have your lock picking kit hanging around in your back pocket. That's where the TOOOL Emergency Lock-Pick Card comes in. It's the size of a credit card and snaps apart to create a full lock picking kit for any emergency. You can't put it back together, but if you need this that often, you probably need to work on remembering your keys better.

You can grab the TOOOL Emergency Lock-Pick Card for $30 at the Maker Shed. Hit the link below to check it out, and as reader process91 notes, make sure to understand the laws about carrying lockpicking tools in your area before buying.

TOOOL Emergency Lock-Pick Card | Maker Shed via Make

If you accidentally lock your keys in the car and don't have your wedge and metal rod handy, you can often unlock the car from the outside using nothing but your shoelace.

This trick doesn't work on every car, but it does work on many, and the older your car, the more likely it is to work. All you need to do is create a slip knot with your shoelace, place the lace at the top right corner of the door, and wiggle it down into the inside of the car. After placing the slip knot over the lock button, you should be able to pull on one side of the shoelace to tighten the knot, pull it up, and unlock the car.

As always, we don't recommend using this to break into a car that isn't yours—obviously, that's illegal (and kind of mean). But, if you lock yourself out of your own car, it's a nice last-ditch effort before you need to call for help. Check out the video above to see it in action, or hit the link below to see the step-by-step process. WikiHow's infographic is also really well done, too.

How to Unlock Your Car with a Shoelace | The Secret Yumiverse

Whether you're stuck inside and need to break out or you've found locked outside and need to get in, having the key or password is rarely your only option. Here are our top 10 favorite tricks for breaking into and out of nearly any locked down environment.

10. Crack an Electronic Safe

Breaking into many types of electronic safes (you know, ones with keypads) is surprisingly easy. You just need to bounce them. It's a pretty simple technique, but looks like it takes a bit of practice. Basically, you drop part of the safe against the table (or whatever surface it's resting upon) while turning the locking knob. If your timing is right, you'll have turned the knob when the safe's lock bounces open for a brief moment. This works because many cheaper safes have locks that lift. Better safes don't have this vulnerability and this trick won't work on them, but if you've got a cheap one and lost your passcode you can just do this bouncing trick to open it right up.

9. Break Into Your Garage from the Outside

Can't get into your own house? Got a garage? Just stick a long metal wire with a hook on the end through the door to grab the garage door latch and force it to lift the door open. You can get back into your garage in seconds with this trick. (See the video to the left for a demonstration.) If you'd like to prevent people from doing this to you, all you need to do is bind your opener's quick door release lever with a zip tie. This will make your emergency latch a bit more difficult to open, but you won't have to worry about any troublesome individuals breaking into your garage with this trick.

8. Release a Sliding Chain Lock with a Rubber Band

If you want to find your way into a door that's bound shut by a sliding chain lock, all you need is a rubber band. Assuming you've bypassed any other locks already, just open the door as much as you can and tie the rubber band to one end of the sliding lock. Next, pull the rubber band down to the door handle. Shut the door and open it again and the door handle will pull the sliding lock out of place. (See a video demonstration here.) Easy!

7. Break Out of a Car Submerged in Water

Perhaps you decided to drive your car into the ocean. It seemed like a fun idea at the time, but now that you're sinking and up against the prospect of death you're feeling a little remorse. Your best bet for breaking free is breaking the window with a device called a center punch. They're cheap and easy to acquire, so you might want to keep one in your vehicle in case of emergency. Failing that, it is possible to kick a window out when you don't have the necessary technology. Just aim for the hinges, rather than the middle, and you should find success with a little luck and sufficient force. Just don't try to open the door. That's just not going to work.

6. Escape from a Car Trunk

For those times when you've been shoved in a car trunk, there is a simple way to break yourself out. Because pretty much every trunk lock has a hook latch, you just have to locate the lock cylinder connected to latch mechanism and use it to release the latch. (More info here.) Many cars have internal releases, however, so you can generally get out by just pushing a button.

5. Unbind Your Bound Wrists

Tied up and bound? No problem. Whether you've been handcuffed or your captor decided to take the cheaper route and go with the more-affordable zip tie, you can still break out pretty easily. To break out of zip ties you just have to slam your bound fists against your butt and pull them apart. Getting out of handcuffs requires a little extra work, in that you need something called a survival strap that has a clasp doubling as a handcuff key. Tricky!

4. Break Into a Windows or Mac Computer

Perhaps you've forgotten your computer's password and need access or you just want to learn how people can break in so you can prevent it from happening to you. We've got guide for both Windows and Mac OS X to help you learn both sides of computer security. Your files are easily accessible with just a Linux Live CD and there are plenty of other methods, like brute-force attacks, that can provide unwanted access, so learn all about it and keep your data safe.

3. Break Into Your Car

Did you lock your keys in your car again? All it really takes to get back in is a wooden wedge (like a doorstop) and a long metal rod. You just use the wedge to pry open the driver's side door just a bit so you can stick the metal rod in the opening and press the unlock button (or whatever it is). I tried this on my own car and was able to actually do it, although it was a bit complicated because the button is rather round. If you have old school locks that push up and down you can just use a crimped plastic strap to lift the lock instead. Remember to be careful and only break into a vehicle that you own!

2. Crack Wi-Fi Passwords

Wi-Fi passwords help secure your network, but they're not that hard to crack. A tool called Backtrack can crack WEP passwords and Reaver can crack WPA. With these tools, the process is fairly easy but a little time consuming. It can take many hours. If you want to learn how it works and how you can protect yourself, check out our Backtrack WEP-cracking guide and our Reaver WPA-cracking guide.

1. Pick and Crack Most Locks

Lock picking and cracking skills are incredibly useful when you lock yourself out of your own home. They're also great for assessing the security of any given lock. We've shown you how to both crack a master padlock and pick pretty much any standard lock. (You can also find video demonstrations in our first and second evil episodes of the Lifehacker Show.) These skills are surprisingly easy to learn. Just use them for good and not evil.