The Shunt is a piece of
climbing equipment made by
Petzel. It is a medium sized
ascender. It allows
one way movement up a rope. While your weight is on the
shunt it lock onto the rope. When you take your
weight
off the shunt you can move it along the rope.
Usinf a combination of shunts you can
load them alternativly and hence shimmy up the rope.
The traditional method for doing this involved tying
prussock knots onto the rope. The shunt is more reliable and easier to use. The drawback is that it is quite a bit heavier than carrying a few prussock loops with you.