On both my E34s I seem to have a vertical black plastic tray beneath the right rear seat (not under the seat, just below it) and you can pop the top off and there's what looks like a 10mm bolt.

i only noticed this as when inspecting one of the cars I noticed a hole there and in the boot were the plastic bits and bolt which fitted in there.

Now can someone please tell me what the hell this is for ?

I also found a round tool in the boot with these bits that looks a bit like a round chrome 'allen key, but without any hex, its just round' - anyone know what this is and if its connected to the 'hole' or vertical tray ?

Cheers.