850 rear suspension

[stevo]

I am trying to chang my rear springs and shocks on my volvo

when trying to undo the lower spring retainging nut the whole bolt rotates

how do i stop it rotating is there a special trick to this.

also when i compare the new rear shocks with the old they look different much wider at thet top

are they correct or does my cAR have nivomat self leveling suspension

any help would be welcome

steve