what you wanna do if iuts sagging down is pull the headliner out of the truck, take a wire wheel on the end of a drill and clean off the old material and foam , so all thats left is the cardboard board. then lay the new material over it, fold back and glue the board then glue the material , DO NOT spay heavy on the material. and do not use glue from an arosole can , it sucks to clean up if you mess up. also when your done glueing the headline flip it over and glue a one inch strip all around and fold material over ..... any more questions pm me please