I have put in new glass and window channel. I am now putting on the inside window trim pieces which consist of two pieces and a clip which fit around the window opening. No problems but I am wondering is there a molding or gasket which fits into the very top of the door to "catch or lock in" the window frame which is metal? This would keep it from rattling or possibly hitting the door or the door trim? Is it possible nothing goes in there and I am trying to create something GMC did not put in? Any comments appreciated. Doug