Hi All and sorry for what seems like a stupid questionMy expo rack has two bars fitted on the top like the one in this picture.

My question is, can they be moved along the rack?
Looking at them logic would say yes but I cannot find anything to loosen them off to allow them to slide along the rack.
I have checked the fitting instructions for the Expo on the and Rover Owners site but the instructions don't even mention such a cross bar
Thanks all,
Ian