To unlock a door with a keyhole you can pick the lock with 2 bobby pins.
How to unlock a door lock with a knife.
Bend the closed end of one of the bobby pins to form a 90 degree angle.
You may need to turn the screwdriver in order for the door to unlock.
To unlock this kind of a door you should be able to take a butter knife or putty knife and manipulate the latch enough to retract it and open the door.
The simplest lock to open though is the kind with the push button as the locking mechanism.
The levers on many knives feature.
Knife makers use a variety of different mechanisms to lock a pocketknife in the open position and each type closes in a different way.
Just insert the screwdriver into the small hole and press the button on the inside of the handle with it to unlock the door.