It depends on what kind of car you have!
This may sound like a dumb question, but are you sure you have the right key? If you are, there are a couple of option. If that key doesn't work in any of the doors, the key may just be worn. It may be a poor copy, or just been used too much.
A competent locksmith will be able to visually decode the key and "code cut" a factory original bringing back to how it is supposed to be. This will likely solve your problem.
If it's just that one lock that is a problem, there are a couple things to try. First, flush it out with WD-40 to try to get any dirt that has possibly built up in there cleaned up. Run the key in and out several times, and try to turn it. Be careful not to force anything.
If the lock will still not turn and you have cleaned it the best you can and made a code cut key (if you needed a code cut key here in Fort Collins it would only cost $10 to $20), there might be a problem with the lock, for example a bent wafer (wafers are the tumblers that "read" the key). The door panel will probably have to be removed and the lock taken out and serviced by a locksmith. Good luck!
Source:
http://www.locksafesystems.com
Take your key and stick it into the lock on the door and turn.
Stick the key in the door lock and turn.
The power locks can only be engaged from the driver's door. You press down on the door lock on the driver's door and it will lock all the doors. Or you turn the key in the lock to the right in the door lock of the driver's door and it will lock all of the doors.
The answer is a key
The door lock may not turn due to a mechanical issue, such as a misalignment of the lock mechanism or a worn-out key. It could also be caused by a faulty lock cylinder or a problem with the key itself.
To fix a door lock that won't turn, try lubricating the lock with graphite powder or WD-40. If that doesn't work, the lock may need to be replaced by a professional locksmith.
To effectively lock a door using the method of "how to lock door," follow these steps: Close the door securely. Turn the key in the lock (if applicable) or engage the deadbolt. Check that the door is locked by trying to open it from the outside. This will ensure that the door is properly secured.
door, doom, loom, look, lock
Insert key in the door lock and turn to unlock the door.
put in the key turn it right and pull out :) !
A door lock is typically considered a combination of a lever and wedge simple machines. The lever is used to turn the lock mechanism, while the wedge secures the door in place when the lock is engaged.
usually you just stick the key in the door and turn the key as if to lock it. try both the driver and passenger doors.