Not only does the window frame trim out the inside of the glass, but it gives the urathane adhesive about 75% more surface area to bond to. The window frame also hides the squeeze out from the urathane. Autoglass Express installs my glass and they use a foam dam to keep the squeeze out from being visible.
The picture is of the frame for the large back glass. The frame for the small back glass looks just like it, but smaller. I still gotta get a pic.
The window frame for the small flush mount back glass is now included with the glass.
The frame installs on the inside and gets tack welded from the outside. I tack weld it about every 4”. If your truck is already painted, glue the frame in place with panel bond.