1. Raise the door to a comfortable height to take your measurements, beginning with the length of the garage door. Add 1-inch for each side to allow for adjustments. Measure the width of the bottom of the door and the width of the existing garage door gasket, if possible. Don't remove the bottom seal completely until you have purchased a replacement gasket.
   
   
2. Remove the existing gasket (or bracket if replacement is necessary) using the screwdriver to back out any screws. Be careful not to dent or damage the steel garage door.
   
   
3. Install the new gasket by sliding it into the existing bracket sleeve. The gasket should extend about 1-inch longer than the door ends on each side. Attach the gasket to the bottom of the garage door using screws. It's best to use existing screw holes if possible to limit damage to the insulation of the garage door.
   
   
4. Trim any excess length of the gasket with a utility knife or hand saw. Be careful not to damage the surface of the door when trimming the excess gasket. Make sure the gasket doesn't impede the raising and lowering of the door.
   
   
5. Test the new garage door gasket seal by lowering the door and checking for a continuous seal along the bottom of the door.

Some garage door replacement gaskets can be quite difficult to find. Consult your owner's information for the correct model of garage door. Garage door gaskets can be very different and certain types are used for particular models of doors. Make sure to release the garage door from the garage door opener before attempting to raise the door by hand.