Straighten one end of a large paper clip. Grab the outside end of the paper clip and bend it away from the rest of the clip. The rest of the paper clip becomes a handle for the straight end. If a paper clip is not available, find a finishing nail or similar long thin item.
Insert the straight end of the paper clip into the hole in the center of the door handle. Once you feel resistance, grab the doorknob with your free hand.
Push the paper clip into the resistance while turning the door knob with your other hand. The resistance is the back of the push-button lock. You will hear the lock pop out and the doorknob will turn.
Insert a small flat screwdriver into the slot in the center of the doorknob. The hole in this type of doorknob might also be round. Use the smallest flat screwdriver possible.
Wiggle the screwdriver inside the doorknob, twisting the handle as you push it through the doorknob. Use the screwdriver to feel for a small slot. Once you find the slot, the screwdriver will offer resistance when twisting.
Hold the doorknob in one hand and turn the knob as you twist the screwdriver to unlock the door. This might take several attempts.