Remove the door from the jamb before replacing the bottom weatherstrip. For inswing doors, with the door closed, remove the hinge pins with a punch. Carefully open the door and remove it with the help of an assistant. (Picture 1)

Place the door, interior side down, on two padded sawhorses. Make sure the door surface will be protected from scratches. Use extra caution if the door has a window. Using a flat screwdriver, pry the existing bottom weatherstrip from the bottom of the door.(Picture 2)

Apply a bead of high-quality, exterior-grade caulk along each end of the weatherstrip on the side with the two barbed seals.(Picture 3)

Insert the barbed seals in the kerfs on the bottom of the door.(Picture 4)

Use a rubber mallet or a block of wood and a hammer to seat the weatherstrip flush with the bottom of the door. Do Not directly hit the weatherstrip with a metal hammer. With a damp cloth, remove excess caulk from door and weatherstrip.(Picture 5)

Replace door in frame. Test the door for proper operation. If your door has an adjustable threshold, you may want to adjust it to compensate for the new weatherstrip. Adjust your threshold according to the instructions provided with your door. Make sure not to raise the threshold too high, as the door may bind or drag and cause bottom weatherstrip damage.