retorquing roof rails?

[kenyee]

Does anyone (Gilly? :-) know how to do this?
Supposedly it fixes a popping noise in the roof when driving over bumpy roads.

My noise is intermittent, so the techs can't seem to reproduce it when I bring it in for this. It's a bit annoying since it sounds like someone is thwacking your roof w/ their finger :-P