Commando valve covers

I'm looking at a set of later 273 Commando valve covers (rubber grommet PCV) and the passenger cover has a bracket attached to the side. I know it belongs there as I have seen it on other sets,but,just exactly what does this bracket hold,or what does it do? Is there a plastic piece that attaches to it to hold something up?..or down? I have attached a pic I found showing the bracket...

Thanks guys!!