I used to do a lot of rock climbing in my younger days. Most fellows would be well advised to learn how to use a Prusik knot (hitch). With a couple of short pieces of cord, even shoelaces in an emergency, a fellow can tie this hitch and climb up. There are a couple of improved versions but the concept is the same. The hitch slides on the rope until weight is applied, then it grips tightly.

http://www.chockstone.org/TechTips/Prusik.htm