“Won’t close” can describe two different failures: a door that cannot fully enter the frame and a door that reaches the frame but the latch does not catch. Separate those cases before adjusting hardware.
First see whether the slab reaches the closed position
Close the door slowly without slamming it. If it rubs at the top, bottom, or side, fix that contact first. Tighten hinges and check for swelling or paint buildup before touching the latch.
If it reaches the jamb, watch the latch bolt
The spring-loaded latch bolt on the edge of the door should enter the opening in the metal strike plate. Close slowly and watch whether the bolt hits high, low, or to one side.
Shiny impact marks on the strike plate often reveal the contact point. A small pencil or tape mark can also help show where the latch lands.
Check screws and sag before moving the strike
A loose hinge changes the position of the entire door and can shift the latch several millimeters. Tighten hinge screws first and make sure the strike plate itself is secure.
Adjust the strike only for a small alignment problem
If the door hangs correctly and the latch misses by a small amount, moving the strike plate slightly or carefully enlarging its opening may solve the problem. This Old House identifies strike-plate misalignment as a common reason a door has to be slammed to latch.
Make small adjustments. Moving the plate too far can leave the door rattling or barely engaged.
Test the knob or lever mechanism
With the door open, operate the handle and watch the latch retract and spring back. If it sticks, remains retracted, or the handle is very loose, the latch mechanism itself may need cleaning or replacement.
Exterior doors have a security consequence
A front or exterior door that will not latch or deadbolt reliably is more than an annoyance. If the frame is warped, the lock is damaged, or you cannot obtain solid engagement, get professional help rather than accepting a partial latch.
A correct door should close without force
You should not need to lift, kick, or slam the door every time. If force is still part of the routine, the underlying alignment or hardware problem is still there.
Sources
- This Old House — How To Fix a Door Latch — Guidance on strike-plate alignment and latch troubleshooting.