Finish carpentry gets fussy in the corners: one jamb out of square, one casing that has to land on the same reveal all the way around, one miter that opens up after the nail goes in. The useful tools in the This Old House archive are not a truck full of gear. They are a square you can trust, a way to steal an odd angle, and a saw and nailer that repeat that angle without a second guess.
A square you set once
A combination square (opens in a new tab) earns its place when the same measurement happens twenty times. Set the blade, lock it, and mark the offset on every door jamb or window casing. The same head, flipped to the depth rod, checks a dado or a rabbet without a second tool. In the Season 23 tool segment the heavier square was the one that stayed true. Weight is not a personality. A light square that has been dropped out of square will copy that error onto every board.
The magnetic combination square (opens in a new tab) drops the thumbscrew. Magnets hold the blade, which is faster when you are walking from opening to opening. It is also easier to leave on a sill. Treat it as the same measuring tool, not as a different method.
Odd corners without a bevel
Walls are rarely 90 degrees. The slow method uses a compass (opens in a new tab) and a sliding T-bevel (opens in a new tab): scribe the arcs, transfer the angle, walk to the saw, and hope the second board matches. The Season 25 trim segment replaces that trip with matching boards and a pencil (opens in a new tab). The boards have to be exactly the same width or the line is meaningless.
- Lay one board flat against the wall at the corner.
- Stack the second board on top, tight to the other wall.
- Hold both down and draw along the edge of the top board onto the board beneath.
- Line that mark up with the opposite corner of the board. That line is the bisected angle.
- Set the miter saw (opens in a new tab) to the line and cut both pieces so you can test the joint before you commit to the long stock.
- For the other end, flip the board and cut from the same saw setting instead of tilting the saw back the other way.
The same sequence works on an inside corner. When the joint closes, you can skip the caulk and the joint compound that were only there to hide the gap. If the boards are not the same width, the line is a lie. Check that before you draw.
The saw itself shows up again on window trim: factory-painted casing, cut on the miter saw (opens in a new tab) and fastened with a nail gun (opens in a new tab). Pre-painted stock is sealed on the back, which field paint often misses. Historic profiles — ogees, beads, coves, fillets — still have to be matched by a millwork shop. A stock knife will not reproduce an 1890s cutter.
What the saw requires from you
A closet build in Season 24 is the plain safety version of the same saw. Eye protection (opens in a new tab) and hearing protection (opens in a new tab) stay on. The board sits tight to the fence. The start is a thumb slide plus the grip trigger, and the free hand stays clear of the blade. None of that is optional because the cut is short.
Installing a room of trim is intermediate work: the layout is learnable, the nailer and the saw are not beginner toys, and a wall full of old profiles is often a shop order rather than a Saturday rescue. For the joint after the miter, the caulk choice is a separate decision. See which caulk belongs in which joint.
Where to watch the source segments
- Season 23, Episode 4 — combination square, magnetic square, depth checks.
- Season 25, Episode 1 — the equal-width miter, inside and outside corners.
- Season 47, Episode 16 — painted window trim, miter saw, and nail gun on the Needham house.