When a door fails to latch properly, it usually means the door is out of alignment. Often, the latch bolt is not dropping smoothly into the center of the strike plate.

If the latch bolt is too low or too high, the problem usually can be corrected by shimming a hinge to realign the door. If the alignment is fine but the door still won't shut, the door may be warped.

Suspending the door between two sawhorses and weighing down the center may counteract the warp, but you should think about buying a replacement door.

1. Fix and tighten any loose hinges and test the door. If the latch bolt still doesn't catch, you can fix any minor alignment problems by filing the strike plate until the latch bolt fits.
   
   
2. Check the door for a square fit. If the door is badly tilted, remove the door and shim either the top or bottom hinge to correct the problem.
   
   
3. If necessary, you can raise the position of the latch bolt by inserting a thin cardboard shim behind the bottom hinge. To lower the latch bolt, shim behind the top hinge.