Stock extenders are hexagon-shaped, so if you look closely you can see it rotating. What I usually do is put on the extender without rotating at all to see which way the attachment point is going. Then I remove that extender, and put a new extender, rotating the second one to the relevant position.
Alternatively, you could try out DSL or Ironforge, both of which have square extenders with attachment points on all sides, so it's way less of a pain.
I think there is a skin pack or something that adds a mark to the proper side of the extender, but I donno where it is.
Good luck!
