Things You'll Need
A strike plate -- the metal plate affixed to a doorframe with an opening for a door latch or deadbolt -- that needs repair will show itself when the door lock's latch bolt misses the hole in the strike plate, or when the door won't stay latched or closed. This can be caused by the shifting and settling of wood frames over time. To correct the problem, adjust the strike plate so the latch bolt lines up and can engage properly.
Determine which edge of the strike plate that the door latch bolt is striking, causing the latch to miss the hole. Mark this spot on the strike plate, using a piece of chalk. Remove the screws from the strike plate, using a screw driver, and pry the strike plate off the jamb.
Clamp the strike plate in a vise, with the strike plate positioned so that the edge that the latch bolt strikes is nearest the vice jaws. File the strike plate down to the chalk mark, using a flat file.
Install the strike plate on the jamb, installing the screws with a screwdriver, and shut the door. Check to make sure the latch engages. If the latch does not extend far enough into the strike plate to engage, proceed to step 4.
Remove the strike plate screws, using the screwdriver, and pry the strike plate from the jamb. Place the strike plate on top of a piece of thick cardboard, which is to be made into a shim.
Outline the strike plate on the cardboard, including the opening and screw holes. Drill out the screw holes in the shim outline, using a power drill. Cut out the shim from the cardboard, using a utility knife. Cut out the opening within the shim using the utility knife, also.
Position the shim behind the strike plate on the jamb. Install the screws through strike plate and jamb, using a screwdriver. If the screws are now too short, due to the added length caused by the shim, install new screws of the same diameter but with a slightly additional length.
Shut the door and check to make certain that it now latches properly. Remove the strike plate and add an additional shim, if necessary for the door to latch.