A door sweep is an excellent way to prevent drafts and cold air from seeping in from underneath an exterior door. Door sweeps can be as simple as a piece of rubber that is attached to the bottom of a door or as elaborate as an actual brush that not only prevents air from coming in from under the door, but also sweeps the area in front of the door as the door opens and closes.
Installing the Sweep:
Purchase a door sweep that is the appropriate width for your door. Generally, door sweeps are the same width as the door. If you do not know the width of your door, then measure the door across.
Using a power drill, attach the sweep to the bottom of the door. If you have a steel door, you will need to use a pre-drill holes with a bit designed for cutting into metal.
Most door sweeps come with screws and holes already drilled into the sweep.
Close the door and check to see that the sweep is preventing drafts and air from coming in under the door and that the door easily opens and closes.