What is this thing?

My Dad is a mechanic and, whilst I am not, I've spent some time watching cars be disassembled, that looks to me like a plastics plug. So underneath your car is a whole heap of plastic lining that kinda seals off the underside, in parts, like mud flaps but for the wheel wells and front underside. Those plastic nubs on the end are plastic screws / plugs, to attach the plastic to the metal body, via a trim edge. That particular part looks like a bracket form of the plastic screw / plugs. Just check the plastic isn't lose or bowing down near the wheel well where you got it from. It would be almost impossible to see where it goes without getting it up on a hoist.