In this video, This Old House general contractor Tom Silva replaces an old entry door.
1. Measure the old door to determine what size to cut the new door.
2. Clamp a straightedge to the new door and score the cut line with a sharp utility knife.
3. Cut the door to length with a portable circular saw.
4. Set old door on top of new door and transfer the hinge-mortise locations to the new door using a combination square.
5. Use a utility knife to score the outline of the new hinges onto the edge of the door.
6. Cut the hinge mortises with a hammer and ¾-inch-wide wood chisel.
7. Set the hinges into the mortises and then drill pilot holes for the hinge screws.
8. Screw one leaf of each hinge to the door.
9. Remove the old hinges from the doorjamb, and replace them with remaining leaves of the new hinges.
10. Place the door into the opening and drop in the hinge pins.
11. Close the door and check its fit in the opening. If necessary, use a block plane to shave a little wood off the door edge.
12. Use a template and drill with hole saw to bore the lockset holes into the face and edge of the door.
13. Chisel shallow mortises into the door edge for the striker and deadbolt.
14. Install the lockset and deadbolt.
15. Check your work by closing and locking the door.
16. Paint or stain the door, as desired, making sure to coat front and back surfaces, top and bottom ends, and both edges.