The klemheist is another in the family of prusik knots - sometimes known as slide-and-grip knots. Like the prusik knot, when weighted, it grips the rope that it is tied around. When the weight is removed, it is free to slide. This enables it to be used in a number of self rescue situations.
The knot must be tied with a rope of diameter less than the main rope, as the effectiveness of the knot is reduced the closer the two ropes are in size. 6mm cord around double 9mm abseiling rope is usually sufficient.
The number of turns can be adjusted to suit the conditions. More turns means greater friction.
The description assumes that you are tying the knot with a prusik loop (a short piece of cord tied into a loop).
Make a bight with the end of the cord, and pass it over the main rope.
|Pass the end with the knot around the main rope once...|
|... twice ...|
|.. and three times.|
|Now, feed the end with the knot through the original loop at the top.|
|Pull the knot tight and set it neatly.|