directions. Most mechanical rope-grabs work like a ratchet, moving freely up the rope, but grabbing when a load is placed down on them. Traditional Prusiks (such as those shown below) will grab when pulled by the tail, either up or down, and will slide either way when pushed by the barrel. Although the Prusik Climb technique may be seen as outdated by some, the US Army still includes it in its annual Best Ranger competition. Rangers in the competition routinely make it up a 65-foot rope in under a minute. Disadvantages Prusiks are ineffective upon frozen wet ropes. This is due to the necessity of friction for the Prusik to function. Mechanical devices (such as jumars) to grab the rope are available that are easier and faster to use, but heavier, more expensive, and bulkier. After being put under a great deal of weight, the Prusik can be quite constricted and difficult to untie. This varies, depending on the relative diameter of the ropes. Related hitches and equipment Although Prusik can be used in a general way, the Prusik hitch is a specific hitch. The two main alternatives are the Bachmann knot and the Klemheist knot (see also the Tarbuck knot). Each has its advantages and disadvantages, mainly in how easy they are to use for climbing a rope. Another variation is the autoblock or French Prusik, used by some people as a backup knot while rappelling. A Purcell Prusik is a related cord popular among cavers and rope-rescue people. A somewhat longer loop than the normal Prusik is used around the rope, then a second Prusik is used around the cord loop itself to form a foot loop. The foot loop is then easily adjusted in length and position. A Prusik-Minding-Pulley is common in rope rescue. The rope to be pulled is passed through a pulley, and a Prusik is tied on the loaded side. When the rope is pulled, the Prusik rides against the pulley, and the rope slides through it; but when the rope is relaxed, the Prusik slides away from the pulley and grabs the rope. Thus, the combination acts as a ratchet (or Progress Capture Device (PCD)). The Farrimond friction hitch is a kind of taut-line hitch that is similar in form to a Prusik. Equipment A Prusik loop is made of narrow but strong nylon accessory cord tied into a loop using a double