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An extension ladder. A ladder is a vertical or inclined set of rungs or steps commonly used for climbing or descending. There are two types: rigid ladders that are self-supporting or that may be leaned against a vertical surface such as a wall, and rollable ladders, such as those made of rope or aluminium, that may be hung from the top.
A pulley may have a groove or grooves between flanges around its circumference to locate the cable or belt. The drive element of a pulley system can be a rope, cable, belt, or chain. The earliest evidence of pulleys dates back to Ancient Egypt in the Twelfth Dynasty (1991–1802 BC) [1] and Mesopotamia in the early 2nd millennium BC. [2]
A A-grade Also aid climbing grade. The technical difficulty grading system for aid climbing (both for "original" and an adapted version for "new wave"), which goes: A0, A1, A2, A3, A4, A5 and up to A6 (for "new wave"). See C-grade. Abalakov thread Abalakov thread Also V-thread. A type of anchor used in abseiling especially in winter and in ice climbing. ABD Also assisted braking device. A term ...
A Z-Drag or Z-Rig is an arrangement of lines and pulleys, effectively forming a block and tackle, that is commonly used in rescue situations. [1] The basic arrangement results in pulling the hauling end 3 times the distance the load is moved, providing a theoretical mechanical advantage of three to one .
Showing the telescopic principle, an object collapsed (above) and extended (below), providing more reach. Telescoping in mechanics describes the movement of one part sliding out from another, lengthening an object (such as a telescope or the lift arm of an aerial work platform) from its rest state. [1]
It is the use of spreaders (long treads that extend well past the vertical ropes) in a pilot ladder that distinguishes it from a Jacob's ladder. When not being used, the ladder is stowed away, usually rolled up, rather than left hanging. On late 19th-century warships, this kind of ladder would replace the normal fixed ladders on deck during battle.