Open your garage door fully. If you use a garage door opener, unplug the power cord from the ceiling after you raise the door. This prevents someone from accidentally closing the door while you are working.
Remove the roofing nails securing the rubber astragal to the bottom of the door. Use a claw hammer, if you have a wooden garage door.
Bend open the ends of each astragal track with a flat-head screwdriver, if you have a steel or fiberglass garage door. The channel has two tracks that the astragal slides into. Installers typically pinch the ends of the track with pliers to prevent the astragal from coming out during operation.
Grab the end of the rubber astragal, and pull it out of the tracks.