STEP 2 Trim Door Opening
Trim any excess drywall around the doorway to make sure the new door will hang plumb.
STEP 3 Check That Floor is Level
Mark for any shims that are needed under the level.
STEP 4 Determine Location for Shims
Measure and mark against the jamb where any shims are needed.
STEP 5 Remove Packing Material
Remove the plug that comes on the pre-hung door, as well as the temporary trim on the bottom of the door.
STEP 6 Position Door
Place the door inside the opening. Position the door so it is plumb, and the door is able to swing open.
STEP 7 Secure Jamb
Secure the jamb with nails along its length.
STEP 8 Check and Adjust Door Opening
Use a straight edge to check the door opening, ensuring that it has room to open and close. With the door closed, place a shim by the bottom hinge to accommodate any adjustments.
STEP 9 Check Top Gap Above Door
Also, check the door again to make sure it is level.
STEP 10 Nail Door in Place
Check the center shim and the gap to make sure the door is plumb. Nail the door in place, from the jambs through the shims.
STEP 11 Fill Nail Holes
Use a nail set to set the nails beneath the wood, creating a smooth finish. Fill the holes with spackle.
STEP 12 Open and Close Door
Check the door to make sure it opens and shuts properly.
STEP 13 Make Adjustments
Place a level on the vertical surface to check that the door is plumb. If you need to adjust the door, try using a sledgehammer with a very gentle tap.