Rear Cab molding mounting question.

[Rufas]

I can usually figure out how to mount moldings. But this one has me stumped. Is the gray plastic clip mounted on the truck first then the molding snapped on? Or is the plastic clip inserted into the stainless steel molding and somehow snapped to the stud on the cab?

There are also two small 'wings' on the plastic clip. It looks like these will be visible when installed.

All I really understand is the clip is pushed on the stud and the pushed either left or right to lock it on the stud.

Any help will really be appreciated.

TIA
Rick