Hi folks! I came across this plastic guide or wedge or whatever you call it. It sits on the bottom of the rear door glass SS trim. I am not sure but I think its purpose is to “block“ the glass in the run channel and keep it from rattling when glass is fully lowered into the door. Or is this wrong? However, I miss this plastic piece on the passenger side. Driver‘s here. Do I really need it? The FSM nowhere mentions this thing.