I'd like to remove the standard roof channel covers to make sure there isn't a build up of dirt creating any potential rust traps. I managed to work out the two rear plastic rivets are threaded, got them out and then started to lever the cover from the rear thinking it would pop off but it looks like it stuck down with adhesive. Are these covers not supposed to be removable? 
Hung like Einstein, smart as a horse.

Stuck down with double sided tape, I discovered when one of mine started to come adrift at the front. If you search on here for roof bar fitting you may get more info.

Ok thanks, guess I'll be best to leave it alone then, at least until decides to peel itself off naturally. 
Hung like Einstein, smart as a horse.