Roofing

Snapping a two-end chalk line so finish fascia installs dead straight over imperfect framing.

Leaving the siding joint over head flashing uncaulked — it's the drainage exit for water that gets behind the siding.

The two rafter angles: the plumb cut matches the pitch angle, the heel cut is its 90-degree complement, plus the bevel when meeting an existing roof.

Laying out a common rafter's plumb, seat, and tail cuts with an oversized square — the pitch scale for plumb, the slot for level.

Placing shingle nails so the water channeling down every butt joint above never crosses a nail hole.

Offset blocks, a string line, and a gauge scrap that pull a long fascia run dead straight when there are no rafter tails to cut to a line.

The flashing at the bottom of a roof-to-sidewall run that diverts runoff into the gutter instead of down the siding.

Slipping a flashing piece behind each siding butt joint instead of relying on caulk.

Pitching a rough sill with a back dam so water that gets past the window drains out instead of soaking the framing.