- 1). Pull up the old threshold if there is one. Unscrew the screws with a drill; if it is nailed in place, use a pry bar to loosen it. Scrape off any caulking with a putty knife so that you have a clean surface for the new installation.
- 2). Lay down a layer of construction paper, also called felt, then place the flashing down on top of it. Trim the felt to fit the opening.
- 3). Bend the outer edge of the flashing up, and place a bead of caulking underneath. Bend the flashing back down onto the bead of caulk. Run another bead of caulk along the back side of where the threshold will go.
- 4). Place down the new threshold over the top of the flashing. Screw it in place with 3-inch screws.
- 5). Run a bead of caulk along the side edges of the threshold, and let it dry.
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