One end should be larger than the other this goes against the taillight housing. You slip it over the wiring and it is held in place by tightening the taillight to the bracket. The other end just tucks up under the bed. I used clamps with rubber lining to bolt the conduit to my stake pocket on the back side. You can see mine in this picture, sorry I could not find a close-up.
http://www.flickr.com/photos/advance-design_parts_co/8129046885/in/set-72157631867396207/