What roller blind? That chain goes to the flush toilet Volvo installed to compete with the VW Beetles which, being air cooled, carried no water on board and, therefore, couldn't offer that luxury. In those days the Swedes, at home, still kept their toilet tanks up near the ceiling to keep them from freezing; hence, the chain. (Some of you may be old enough to remember when you had them at home too.) If it hadn't been for that, they would have put a lever on the dash, and we would have had to do without that great conversation piece when we open the hood.