From time to time, your doorknob or door handle may require a little maintenance. The constant pushing, pulling and twisting on the handle or knob, plus the slamming of the door, may cause some of the parts to loosen. Before you rush out to the store to purchase a new doorknob, you should investigate the problem further. You may be able to fix the problem yourself, oftentimes with nothing more than a small screwdriver. Check the doorknob handle, latch and strike plate before you make your diagnosis.
Check to see if your doorknob is latching properly; you may need to simply adjust the strike plate. Kneel down and observe the strike plate. Notice any dents above or below the groove where the latch fits.
Align the doorknob. Loosen the set screw on the doorknob. This is the small screw located on the neck of the doorknob, just in front of the inside knob. Use a small screwdriver (flathead or Phillips depending on your doorknob) and twist the screw counter-clockwise one revolution. Hold the outside knob with one hand and turn the inside (loose) knob until it fits tightly. Tighten the set screw back down. Turn the inside door knob to ensure it is not loose.
Shut the door and see if the latch is still hitting high or low on the strike plate.
Remove the screws holding the strike plate in the door frame. Pull the strike plate out of the door frame.
Scrape away some of the wood at the top of the latch groove if the latch hits high on the strike plate. Use a small file to remove enough of the wood to reposition the strike plate.
File away some of the wood below the groove if the latch is hitting low.
Smear a layer of wood putty around the groove if the latch is not reaching all the way into it. This will extend the door frame surface and allow the latch to align properly. Allow the putty to dry for an hour or two before continuing.
Position the strike plate to its new position over the groove. Shut the door slowly to make sure the latch and groove align properly. Open the door and screw the strike plate into place in the door frame. Shut the door and listen for the latch to click.