Vertical caving terminology and methods > Personal SRT gear
An essential part of the inchworm system, and often a part of the hands and feet system, which attaches a handled foot jammer to the feet. The foot jammer is bolted, screwed or tied to the middle of a metal or wooden bar, or webbing tape covered in a plastic tube, wide enough to put both feet on it, so that the foot jammer sits between the feet. A strap or rope then runs from one end of the bar, through the metal loop at the top of the ascender, and down to the other end of the bar, passing over both feet. This is what causes the foot jammer to be lifted when the feet are raised. The foot jammer must have a single metal loop at the top, on one side of the frame only. If the strap has to pass through holes on both sides of the frame, it will not be possible to get the main rope in or out. Mar-bars were almost always custom made by the person who would end up using them, so there is a great deal of variation, and no standard approach for how to connect them to the ascender. Most designs rely on the square chunky frame of a Jumar brand ascender, which also had a single loop at the top. The name is a shortened version of "Jumar-bar", and comes from the USA, but there seems not to be a British alternative.
The idea of two stirrups for the feet, attached to an ascender, was included in the earliest known clamping jaws ascender, which was created by French inventor Nicolas Grollier de Servière, which he called pincers or pliers ("tenaille" in French). The exact date of its invention is not recorded, but it was during his retirement which began in 1642 and ended with his death in 1689. It is likely to have been shortly after obtaining the 1647 French translation of a book by Galileo Galilei, which inspired the inventor's research into rope access. At that stage, the stirrups were an essential part of the operation of the ascender, which needed to me lifted apart with every movement to release the ascender, which was used for the hands and feet system. In 1725, German engineer Jacob Leupold from the Holy Roman Empire (now Germany) added a separate bar with a pair of stirrups to Claude Perrault's ascenders, and used them with the hands and feet system. This exactly matches the function of the mar-bar. A second one was used for the hands, in the same way as the mar-bar was later said to be usable by cavers.
Many subsequent designs used similar approaches with the hands and feet system. In 1879, German inventor Ed. von Mengden used clamping jaws ascenders with the inchworm system, and used foot stirrups for that. In 1963-1964, the British South Wales Caving Club used the mar-bar approach for their version of the hands and feet system, strapping a bar to their recreation of an existing cable ascender. The ascender attachment and the foot plate was made from welded angle iron on one side, with the other side being made from a bicycle pedal, so that it could rotate to pull a lever on the ascender, allowing it to be disengaged. American Charley Townsend then used a mar-bar for his version of the inchworm system in 1965-1966. This time, it used an actual jumar ascender, which is what gave the name to the mar-bar. This became popular enough that several designs were subsequently made, fitting whichever ascenders the user had. The bar itself may be made from metal or wood, and the stirrups may be made from rope or welded metal. American arborist Michael David Gardner of Rope Step Inc. had developed a mar-bar by 1992, which was used for the hands and feet system. The specific design is not shown in detail, but appears to be entirely made of fabric webbing, looped around the feet. Arborist books discussed the use of a mar-bar in 1995, for use with the inchworm system, and had probably done so earlier as well. American arborist Paul Sisson had developed his version of the mar-bar by 1999, for use with the hands and feet system, with the same design being used for both the feet and the hands. Each one had two ascenders next to each other, so it could work with either a single rope or doubled rope. The bar was made of fabric webbing, with lengths of plastic piping put over it for the feet or hands to rest on, holding it into shape. By 1999, this design was being sold by American arborist supply company Buckingham Manufacturing.
This history section only covers mar-bars. This article also has a detailed history of many of the other devices and techniques that are used for vertical caving.
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