A nonworking doorknob points to either a jammed latch or someone locking the doorknob before closing the door. Either way, it leaves you in a difficult situation, especially if it's a bathroom door and the facility inside is needed quickly. Calling a carpenter is one way to alleviate the situation, but a little ingenuity will save you both time and money.
Take an old credit card from your wallet or a card of the same size that is equally flexible. Hold the credit card horizontally in your hand. Push the end of the credit card at a 45-degree angle between the door and the door frame.
Push the card in all the way, making sure you can still hold the card between your thumb and index finger. You will feel the credit card pushing the latch back past the strike plate and out of the door frame. It may be necessary to move the card up or down to connect with the latch.
Push the door to see if it opens, If it does not, wiggle the card slightly until the latch has been freed from the door frame. If you find that the door was locked, unlock it before closing the door.
Straighten out a wire paper clip if you have a doorknob with a small hole in the centre of the handle with a push-in locking button on the other side. While turning the doorknob, push the paper clip into the hole, slightly twisting it. Continue to turn the doorknob, as well as twist the paper clip until the lock pops open.
The strike plate is the metal plate that is screwed to the door frame which has a hole in the middle for the latch to enter through. When the latch is positioned through the strike plate and into the door frame, the door is held in a closed position. Turning the doorknob pulls the latch out of the door frame and past the strike plate, allowing the door to open. As with most things, the more practice, the better you become. It can be helpful to practice opening a door with a credit card, but choose a door that doesn't open to a room that is immediately needed.
Don't use a new credit card because it might damage the metallic strip on the back. You may even choose to keep an old unused card on hand for this purpose.