With the help of the usual staples can open many locks and latches.
This suggests that most of the locks is only a deterrent, some deterrent and do not provide 100% security.
Information for reference, do not try to use these skills for personal gain, only good intentions.
Indeed, it may happen that your child close to you, and will not be on hand key or something else.
Improperly hung doors
Surely you've heard of people who open the door with a credit card. Well, you can do the same thing using a paper clip.
There is a strong likelihood that the door could set improperly. This allows to easily pass therethrough. If the door lock is not installed or it is not functioning properly, the door latch can be let go. This becomes even easier if between the door and the jamb there is a large gap.
If you do not get to push the latch and open the door from the outside, you can use a paper clip to pull the latch from the inside. To do this, start a paper clip to bend his big hook. Then paste it into the crack in the door and bring back the latch. Continues to lead it forward until the end of the clip will come back to the front of the door, and you can not grab him. Clamp both ends of the clip and pull over. The door should open.