Page 121 - Rappelling

fireman’s belay someone down below is attentively the autoblock down as you go, allowing the rope to
holding the rappel rope. When this person pulls freely slide through the knot. When you let go, the
down on the rope and applies tension, the rappeller autoblock knot rides up and grabs onto the rope,
will stop on a dime—he or she cannot move down like your brake hand squeezing the rope. To release
the rope when it is under tension. the autoblock, even with your weight on it, is as
simple as sliding it back down and holding it in the
Rappel Backups “open” position with your fingers. It’s a beautiful
thing, and easy to rig.
In the old days the most common method for a The disadvantage of clipping the autoblock to
rappel backup was using a prusik knot on the ropes your leg loop is that if for some reason you were to
above the rappel device, connected to the harness go unconscious and flip upside down, the autoblock
with a sling. With a prusik, the non-brake hand will ride up and come in contact with your rappel
cups the prusik knot and holds it in a loosened device, which prevents it from grabbing, much like
position during the rappel, allowing it to slide down sliding it down and keeping it “open” with your
the rope. Letting go of the knot allows it to slide up
and grab onto the ropes, stopping the rappel. There
are two drawbacks with this method. One is that for
the prusik to lock off, it must hold all the rappel-
ler’s weight. The second is that once it is weighted,
the rappeller must remove all his body weight from
the prusik knot in order for it to be released, not
an easy task if you’re on a free-hanging rappel. In
essence, to take your weight off the prusik, you’ll
need the skills to perform a mini self-rescue.
The modern rappel backup utilizes the auto-
block knot, which is rigged below the rappel device.
There are two distinct advantages with this method.
One is that for the autoblock knot to grab, it only
needs to hold a very small percentage of the rap-
peller’s weight, since it is on the braking side of
the device, and the device itself is holding most of
the weight and providing most of the friction. It is
essentially like your brake hand squeezing and grip-
ping the rope, and for that reason some instructors
refer to it as the “third hand,” like an angel grab-
bing your rope and averting a catastrophe if for
some reason you’ve lost control of the brake. The
second big advantage of the autoblock method is
that it is releasable under tension (i.e., when you’ve
weighted it and it’s grabbing onto the rope). As you Black Diamond ATC XP is rigged for rappelling
rappel down, you simply form a circle with your with a three-wrap autoblock backup clipped to
thumb and forefinger (like the OK sign) and push the leg loop with a locking carabiner.

110 RAPPELLING

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