The perils of daisy chains

Use with caution! If not clipped in properly, you may be connected to the world only through a few stitches: http://www.bdel.com/vids/daisy_chain_%20failure7.mov

Article on friction knot testing

Dr. Ron Farmer, prompted by Federation Mountain Rescue (European?) tested the relative performance of four knots. In decreasing order of performance were the autoblock, Bachmann, prusik, and klemheist, tested using both 6mm and 7mm cord, for backing up a rappel.

Link to article:
http://www.rockclimbing.com/Articles/General/A_scientific_study_of_common_friction_knots._273.html
NOTE: abseil = rappel