Tighten the screws on the hinges; replace any stripped screws with longer screws or wood screws
Check hinge alignment; remove the door and re-seat hinges if they are misaligned
If hinge holes are stripped, fill holes with toothpicks or wooden dowels and glue, let dry, then reinstall hinges
Tighten the hinge screws again after adjustment
If the sag is caused by worn hinge pins, remove the hinge pin and replace it, or reinstall and apply lubricant
Bend the hinge leaves slightly to correct alignment, if the door is only mildly out of alignment
Add hinge shims behind the hinges to raise or align the door (use thin shims evenly under the affected hinge side)
If the door hits the floor or latch side, adjust hinge placement by adding shims to the top or bottom hinge as needed
Replace worn hinges with new hinges of the same size and type
If the door frame is loose, tighten or replace the frame screws/anchors and ensure the frame is square
Re-shim the entire door frame if the frame is out of plumb or not square
If the latch doesn’t engage, adjust the strike plate position by loosening screws, repositioning, and retightening
If the latch bolt hits the strike plate incorrectly, realign the strike plate using a chisel only if necessary
Test door swing and latch engagement; repeat hinge/strike adjustments until the door closes smoothly without rubbing
Replace the door hardware (hinges and strike plate) if repeated adjustments don’t correct the sag