This text will illustrate step-by-step guide to installing a prehung interior door.
1) If you're replacing an existing door, pry off the old trim, and pry out the side and head jambs. If you're installing a door in a newly framed opening, be sure the framing is sized properly.
2) Set the pre-hung door into place with the hinges positioned on the proper side, and tilt it up into the opening. It's a good idea to have a helper on the other side of the door to receive it and help shift it so the jambs are flush with the walls.
3) Push wooden shims between the jambs and trimmer studs on both sides while checking the jambs for plumb with a level. Tap the shims with a hammer until they're snug.
4) Nail through the jambs and sets of shims with 10d finishing nails. To avoid denting the jambs with the hammer head, stop nailing before the heads reach the surface and finish with a nailset.
5) Install new trim around the door, using 6d (2-inch) finishing nails
