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A ladder is a vertical or inclined set of rungs or , and Rope ladders that are hung from the top. The vertical members of a rigid ladder are called beams (US) or stiles (UK). With a bit of agility, one can slide down the stiles without climbing down each rung. Rigid ladders are usually portable, but some types are permanently fixed to buildings. VARIATIONS Rigid ladders are available in many forms, such as:
Rigid ladders were originally made of Wood , but in the 20th Century tubular Aluminium became more common because of its lighter weight. Ladders with Fiberglass stiles are used for working on or near overhead electrical wires, because fibreglass is an electrical Insulator . For safety, a rigid ladder should be leaned at an angle of about fifteen degrees to the vertical. In other words, the distance from the foot of the ladder to the wall should be about one quarter of the height of the top of the ladder. At steeper angles, the ladder is at risk of toppling backwards when the climber leans away from it. At shallower angles, the ladder may lose its grip on the ground. Ladder stabilisers are available that increase the ladder's grip on the ground. A ladder standoff, or stay, is a device fitted to the top of a ladder to hold it away from the wall. This enables the ladder to clear overhanging obstacles such as the eaves of a Roof , and increases the safe working height for a given length of ladder. Rope ladders are used where storage space is extremely limited, weight must be kept to a minimum, or in instances where the object to be climbed is too curved to use a rigid ladder. They may have rigid or flexible rungs. Climbing a rope ladder requires more skill than climbing a rigid ladder, because the ladder tends to swing like a Pendulum . Dissipative ladders are portable ladders built to ESD ( Electrostatic Discharge ) standard. Electrostatic Discharge is a natural occurrence in which electricity is passed through our body, or other conductor, and discharges onto some object. For example, the shock we feel when we touch a doorknob is an ESD. This natural occurrence is becoming a very hot topic in the field of electronics assembly due to the costly damage ESDs can cause to sensitive electronic equipment. Dissipative ladders are ladders with controlled electric resistance: the resistance slows the transfer of charge from one point to another, offering increased protection during ESD events: ≥105 and < 1012 Ω / square ( {Link without Title} {Link without Title} ) Pool ladders. A ladder is also used on the side of a boat, to climb into it from the water, and in a swimming pool. Swimming pool ladders are usually made from plastic steps with special grip and metal bars on the sides to support the steps and as handrails for the user. HISTORICAL USAGE Ladders are an ancient tool and technology. A ladder is depicted in a nest to harvest Honey . TRIVIA
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