The purpose of this knot is to provide a loop divided into two parts, where the divider can be moved easily
by hand but not easily move by itself. The large top loop goes up and attaches to an ascender, either by
passing through a hole on the ascender or by clipping to a hole. The small bottom loop is placed around your
foot on the same side. The separating knot is then moved down to snug the loop on the foot, so that it's
comfortable but not so loose as to fall off your shoe. The length of the loop is chosen to allow for the
legs to comfortably assist in the use of ascenders to move up a rope.
The key features here are that the total length of the loop does not change when it is adjusted, and that
although the bottom loop is snug around the foot, it DOES NOT tighten when weight is put on it. The bottom
loop is also easy to open up to release the foot, even after significant weight has been placed on the loop.
I've made two variations on this knot. The first variation is based on a "double-fisherman" arrangement with
the addition of the thru-rope, but results in the three inner ropes being in a triangular arrangement, so
there's no way to avoid the thru rope from sliding against the end lead of the two knots. This may present a
small risk that the movement of the thru-rope to adjust foot tention causes one or both rope ends to shift
into their respective knots, loosening them.
The second variation shown is the one that came with my Jumar ascenders so many years ago, and places the
three central ropes in a row instead of a triangle. The twist that makes the knot is identical to the double-
overhand used in the fisherman's knot, but is dressed slightly differently. This allows the thru rope and
end rope to be separated by the static rope that feeds the other knot, which prevents the end rope from being
rubbed while adjusting the fit of the foot loop.
Examples below show both the typical single-rope implementation and a multi-color example that highlights the
paths of the three sections of rope that make up the ascender loop.
Don't rely exclusively on just these loops when ascending. Have either a follower / prussic on the rope to
your harness, or a separate strap/loop from both ascenders to your harness.
