Measure 1 inch up from the bottom of the door on both sides with a tape measure. Mark these points with a pencil. This is where the bottom edge of the metal base plate will sit.
Measure in from both sides of the door 2 inches. Place a mark with a pencil at this point. This is where the edges of the metal base plate will be.
Set the metal base plate up against the door and line it up with the marks. This centering process will keep the door from interfering with the weatherstripping on the sides of the door jam and the underlying door sweep and sill.
Screw the metal base plate screws through the holes in the base plate using an electric screw gun. If the plate is adhesive-backed, remove the film from the adhesive strips and stick the plate in place.