In this video, This Old House general contractor Tom Silva installs interior window trim using hand tools.
1. Mark the location of each side casing on the wall.
2. Measure and crosscut the window stool to length from 1x4 primed pine.
3. Rip the window stool to width using a handsaw.
4. Use a pencil scriber to mark a notch on each end of the stool.
5. Saw the notches from the stool so it fits snugly around the window stops.
6. Round over the sharp edges and ends of the window stool using the block plane and 120-grit sandpaper.
7. Fasten the stool to the window with 2½-inch finishing nails.
8. Tap the nailheads below the surface using a hammer and nailset.
9. Saw the side casings to length, then glue and nail them in place with 2-inch and 2½-inch finishing nails.
10. Nail up through the underside of the window stool and into the bottom end of the side casings.
11. Mark and crosscut the head casing to length.
12. Glue and nail the head casing across the top of the window.
13. Mark and cut the apron to length.
14. Apply glue along the top edge of the apron, then nail it to the wall directly below the window stool.
15. Wipe away any excess glue with a damp cloth.
16. Fill all nail holes with wood putty. Once the putty dries, sand the surface smooth.
17. Wipe away sanding dust with a damp cloth, then paint the trim.