Dome light reinstall. What do I do with the black plastic piece?
 

After I replaced my headliner I don't remember how to reassemble the dome light.
There is a black plastic piece that apparently goes behind the headliner but I don't see why.
The light fits perfectly onto the studs hanging down from the ceiling without it.
I think if I try to put this plate in between it is going to push the headliner down too much.
I have looked for a picture of how it's supposed to be online but can't find anything.

You're probably not going to get much help without pics.

Here's the part I'm talking about
https://cimg1.ibsrv.net/gimg/www.nor...4a670eff43.jpg

Does this diagram help?

http://www.realoem.com/bmw/enUS/show...34#63316962023


https://cimg9.ibsrv.net/gimg/www.nor...980e8e8131.png