How To Fix a Door that Won't Latch
A door that closes properly but won't latch closed may be affected by the weather, or it may result from wear and tear, loose hardware or settling of the building. As the weather changes, wooden doors swell and may fail to latch; for that situation, refer to our article on doors that won't close.
The first and easiest thing to check is that all the hinge screws are tight. If the door is sagging, prop it up first with a magazine or book before tightening the screws. If the wood won't hold the screws tight, one quick fix is to fill the hole with toothpicks. Start by dipping a toothpick in wood glue or any other glue you have around and sticking it into the hole. Keep adding toothpicks until the hole is mostly filled. Use a razor know to cut off the excess. Allow the glue to dry and then the hole will be ready to hold a screw. This is just one quick option, but it shouldn't be used for safety or critical applications.
If the door still won't latch, check that the screws in the strike plate on the door jamb are tight. Inspect the hole of the strike plate for obstructions that may prevent the latch from engaging. Next, on the door, check that the screws to the latch plate are tight.
Press the latch in and let it out. It should slide in and out easily and smoothly. If it doesn't function properly, the door knobs may be installed too tightly against the door, the latch may need lubrication, or the latch mechanism may need to be replaced.
If everything is tight and the latch operates properly, then you may need to adjust the strike plate. Spread a small amount of petroleum jelly on the latch and then lightly close the door and reopen it. The petroleum jelly will transfer to the strike plate enabling you to determine if the latch is aligned with the strike plate. If the jelly is higher or lower than the hole on the strike plate, then the plate will have to be adjusted.
It may be possible to adjust the strike plate a small amount by simply inserting a small scrap of wood into the opening and hammer the wood to drive the plate up or down. If a greater adjustment is necessary, then you will have to remove the strike plate, chisel out enough wood to accommodate the new position for the plate, enlarge the hole for the latch and then reinstall the plate. However, small adjustments may result in the screw following the path of the old screw holes. If this happens, it may be necessary to fill the old holes first. Also, predrilling new holes is also helpful.