unscrew the glass and pull it out, then take the tracks and slide the sliding peice forward( you will see the "hook" at the back that holds the back down) push it against the spring, and crimp the track so it can't slide back. then put a bead of clear caulk on the rubber seal and set your glass on it and screw it back down. that will hold the whole mechanism in it's place. then just fill the gap around the glass with caulk. this will make sense when you get it apart.