When removing my cracked rear side window, I found a plastic skirt laying inside the quarter panel. It consists of a rubber angle strip - like 1/2" angle iron, only made of rubber. It is about 24" long, with about 3" of one end mitered and bent at a right angle. Attached to this strip, is a piece of clear poly that hangs down about 8". The lower window channel is about 37" long
Obviously it is a water shield of some kind. Can anyone tell me exactly how this thing is mounted? Does it mount to the window setting channel? Or maybe along the inside edge of the quarter panel opening? I'm pretty sure it goes outside of the window. Any suggestions?

'Kay, I've added a few photos. The skirt appears to go as situated in photo 4, but there isn't really a flat surface to stick it to. Nor is there a surface inside the window opening of the car. It looks like it could go on the inside of the window channel, but it wouldn't be much good there.
I could pull the other door panel off, but trying to avoid any additional damage and I'd rather not. Can anyone tell me anything about this? Maybe it's not even part of the window?

Thanks to anyone who can help

Mike