User blog comment:Assassin of persia/So those were left for Ezio/@comment-72.197.218.142-20110707095715

The ropes are set up before the beams as construction material. They are there to ensure the people setting the beams don't fall into the canyon. How do you think people got to the other cliffs before the beams came along and made life easy. They are also there for people who aren't as badass as Altair who can balance on round, wooden polls without even a hiccup. :D