Page 34 - D. Raleigh "Knots and ropes for climbers"

Rappel with a Prusik as a backup.

The best Prusik is made from durable, 5- or 6-millimeter perlon cord tied in 1-foot loops and secured
with a Double Fisherman's. Three to four wraps around the rope will usually give the best hold. Add
wraps if the knot slips. In a pinch, I've made Prusiks from almost anything, from 1-inch webbing to 9-
millimeter rope. All work to some degree, but you do have to experiment with the number of wraps to
make the Prusik grip properly. When you are prusiking double ropes, wrap both Prusiks around both
ropes rather than put one Prusik on each rope.

Regardless of what material you use for the Prusik, dress it evenly, weight it slowly, and loosen it well
before you slide it up the rope. All Prusiks have a finite life and will eventually burn through (small
cord is less durable than the fat stuff), so inspect them regularly.

If you use the Prusik to back up a rappel, make sure the sling that attaches the Prusik to the harness is
short and always within easy reach. At least one climber has died because his sling was too long and
locked up out of reach, stranding him on rappel.

Common Uses
Ascending single or double rope
Rappeling backup

Secondary Uses
Tying off belay
Improvising hauling system