Once I have prepared the door for the opening I will place my six-foot level against the side of the doorway where the hinge side of the doorjamb will be placed. I will place door shims at the approximate locations that will be even with the door hinges and slide them in until they are level and tack them in with the nail gun. I will check them with a framing square to make sure the door opening doesn’t have a twisted stud in it. If the opening is twisted I will place the shims with the taper going from the same direction to compensate for the twist. If I need to shift the door over a bit I will make the shims a little thicker. I will check with a tape measure as I go to make sure the door will still fit with room to shim the striker side. With the shims in place on the hinge side I will remove the fasteners holding the door to the jamb and place the door in the opening. With the hinge side jamb tight against the door shims and tight to the floor I check the reveal between the top of the door and the head jamb to make sure it is even. If the gap isn’t even I will remove the door and cut a little more off the necessary side of the jamb to make the reveal even. If the door will sit on a carpeted surface a small gap won’t show so I will slide a shim under the low side of the jamb to raise it until the reveal is even.

   With the hinge side now secured I will move on to the strike side. I will start at the top and slide a shim in from each side until the reveal is even with the reveal at the top of the door. I will close the door and, with the door held tight against the doorstop, I check that the jamb is even with the walls at the top and nail it through the top shim. I then open the door and nail the jamb on that side as well. I will repeat this with the middle and the bottom. I place the middle shims right above the strike plate mortise so I know it will be solid where the doorknob will be located.