Passenger side:-

Driver side (no-bolt and surround is cracked):-

I've noticed a bit of creaking from somewhere behind the driver seat... so maybe the lack of this bolt is to blame?
So, are these just holding the roof bar on or do they serve another purpose?
If they are holding the bar in place, does this mean mines is in danger of coming off with just 1 bolt remaining?
Cheers, as always... Andy.