How is the center grille fastened?

I've got to remove the bumper over the weekend to get the body gaps addressed but I'm wondering about the center grille piece and what holds it in, the outside edges on mine appear to be free floating for whatever reason which is one of the things I want to take care of while the bumper is off.

Does anyone know of fastener points, clips, or have any images that might help explain it?

Thanks!