Prussik Knot

The prussik knot is basically a rescue knot that is used to secure a sling (i.e., a continuos loop of cord) to a larger diameter rope. If weight is applied to the sling (e.g. if someone stands in it), the prussik knot will tighten up on the rope, and the sling will not move. However, if the weight is released, then the prussik will slide up or down the rope.