Open your garage door to a comfortable working height. You can prop the door open using a 2-by-4.
Remove the old weatherstripping by prying it away from the bottom of the door using the claw end of a hammer. Sand the bottom of the door to remove loose paint and splinters. Apply wood sealer to the bottom of the door. Allow it to dry.
Measure the length of the door. Cut the new weatherstripping several inches longer than the door to be sure that you have plenty of length.
Position the stripping along the bottom of the door with the tapered edge facing outward. Tack the weatherstripping to the bottom of the door with 1-inch galvanized roofing nails. Cut off excess weatherstripping with a utility knife.