5. An arch. Obstacles along the way get increasingly difficult to surmount, so you just continue up canyon as far as you can go. I stopped and turned around at a 4th class rock wall. There was a rope there, but I had no way of knowing how old it was or how securely it was tied etc. Also if I decided to use it, there was always the possibility that it wouldn't be there when I returned. The safe thing to do was to turn around and head back.