Vertical caving terminology and methods > Rigging methods and equipment
An expandable scaffolding bar, rod or beam, made from at least two parts, and almost always made from metal. In almost all metal versions, at least one of the parts will be screw threaded or have some other adjustment mechanism. At least one of the parts is hollow, and has the other part inserted into it. There is normally a nut which can be turned with a spanner, handles, or other turning tools to adjust how much of the inner rod pushes out of the end of the hollow rod, changing the length of the stemple. Some designs might need the end of the rod to be spun to extend it, and might use different tools or a lever. Commercial brands include Acrow props, which might be used to hold up the ceiling of a house while building work takes place, but these are excessively heavy. Extending the stemple can be used to wedge the stemple between the walls or floor and ceiling of the passage, wedging it firmly in place. For vertical caving, this might be used in rare cases to provide an anchor in a passage where there is nothing else to attach a rope or carabiner to, or where the integrity of the rock is not good enough for drilling holes for anchors. Alternatively, stemples might be used in very rare cases to act as a fixed aid, providing a foothold which can be stood on while traversing. Using a stemple requires the passage walls to be roughly parallel to each other with some kind of alcove or recess for the ends of the stemple, to stop it suddenly slipping out of place due to the pressure. The passage must also be narrow enough to work with the length of the stemple, and this is limited by the strength and stability of the materials which it is made from. Because of these factors, stemples are far more commonly used while exploring abandoned mines rather than caves. In mining, the word stemple typically refers to wooden beams that are used in a similar manner, with wedges used to extend the length. These are often used to support wooden floors or other structures.
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