Locked doors may be unlocked without a key by using credit cards, bobby pins, paper clips or bump keys. Bump keys are specially crafted devices that are used to pick locks that are based on a pin-locking system, which is common in most homes. Since bump keys only have ridges on one side, they are not helpful in unlocking double-sided locks, such as those installed in most cars.
Credit cards are great at unlocking standard spring locks. To unlock a spring lock with a credit card, the plastic card has to be slipped into the gap between the door and the frame. Once inside, the credit card has to be angled in a way that it hits on the opposite side of the lock first. This causes the credit card to slip between the spring lock and the door frame. This method can be done with any piece of flexible plastic, but it does not work on deadbolt locks.
Using paper clips and bobby pins to unlock doors takes skill and talent. This isn't something that most people are able to do without practicing first. The job may be made a little bit easier by purchasing a lock picking toolkit. Unfortunately, the easiest way to buy a lock picking toolkit is online, but this means that the homeowner has to wait for the toolkit to arrive.