The klemheist knot or French Machard knot is a type of friction hitch that grips the rope when weight is applied, and is free to move when the weight is released.

The klemheist is also a way to attach a snubber to the anchor rope of small boats, with the advantage that it is easy to undo.

Make a secure loop of a cord (see Double fisherman's knot) that is definitely narrower than the rope.

If the knot slips when load is placed on the hanging loop, re-tie around the climbing rope another time or two, until there is no slippage.

Making the wraps slide when the hitch is under tension will create friction heat on the rope and the knot.