on my 2011 bighorn, the flap seal is part of the base that holds the bulb seal.... there is a screw at each end of the bulb seal (look inside the end of the bulb) that when removed, the seal piece can be slid or pulled off the track... and the screws that hold the track/flap seal can easily be seen.... remove them and replace what you need to.... any rusty screws that come out is a place that wasnt sealed completely, so if the base material is damaged and wont hold a screw, it will either need to have a little larger or longer screw in that location, or inject the hole with epoxy, and after it sets up, redrill to fit the new screw...