Removing and Refitting Arch Liners (Front & Rear)

[99PBATR]

As part of my winter spruce up for the Monaro, I have taken off the arch liners to clean and spray up. One thing which baffled me was when I took the rears off. Both had a fixing with a metal flange on the back, which from what I can see, appears to do nothing at all. I have sat and looked and tried to work out why they are there but after scratching my head, I'm none the wiser frankly. Am I missing something here, as they don't appear to attach to the body work in any way or perhaps mine have been bodged and fit wrongly.

Advice would be appreciated on how they are actually supposed to fit