Feeling Stupid - What Is This?

Cleaning out my bed I found this bracket/locker.

I remember getting one in and fighting with this one until deciding i didn't need it at the time (-20°)

I can't for the life of me remember where it goes or even what i was doing at the time.

Warm now, I'd like to make it right.

Thank you

2011 2500 ST

Attachment 11135

Looks like a retainer clip for the license plate light.

That looks like a headlight clip.