The astragal is the strip of rubber that runs along the bottom of your storage door and acts as a barrier seal to protect a storage unit from draughts and dirt. To replace it, simply raise the door so the astragal is even with the latch hole on the side of the guide. Using a flathead screwdriver, open the crimped aluminum on each end of the astragal channel. Slide the used strip through the latch hole and discard. Spray a light lubricant along the inside of the channel and feed through a new astragal strip of appropriate length. Use a pair of vise-grips or pliers to re-cramp the ends.