Install a prehung exterior door by aligning it in the rough opening so that it is level and plumb. Install your knob hardware, and nail the door in place. Replace the trim to complete the installation.
- Align the door
Center the prehung door, with its hinges and jambs attached, in the rough opening so that the space on each side is even. Insert shims into the gaps to hold the door firmly in place. Use a level to check for plumb on both side jambs, and adjust as needed to make sure the door is perfectly upright.
- Install the hardware
Install the knob and striker plate as described in the instructions included with the hardware. To avoid stripping the screws, use a screwdriver to tighten screws, rather than a drill-driver. Test the door to make sure it opens and closes correctly. Adjust the alignment as needed.
- Nail the door
Drive one nail through the door jamb into the wall frame in each corner to hold the door in place. Remove one screw from each hinge, and drive a 3-inch screw through the jamb into the wall frame in each position. Be careful not to fasten them too tight, as this could pull the door out of alignment.
- Install the trim
Measure and cut trim to fit the sides and top of both faces of the door. Align the trim so that the inside edge of the trim is 1/4 inch from the inside edge of the door frame. Nail the trim in place with finishing nails, using one nail for every inch of trim. Fill nail holes with wood filler to complete the project.