The rubber washer goes under the awning rail to preserve the original seal. I think i then put a metal washer,then the awning rail,then another metal washer and then tightened it all down with a loctite nut. Then the roof rails sit over the threaded bar that is sticking up with a washer and a loctite nut to tighten the rails down. I would have a look at the van for you to make sure but its away having a Caravelle floor fitted at the minute,hopefully back this weekend if you still need me to have a look for you.