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Rigid ladders were originally made of wood,but in the 20th century tubular Aluminum step ladder became more common because of its lighter weight. Ladders with fiberglass stiles are used for working on or near overhead electrical wires, because fiberglass 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 stabilizers 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 Aluminum step ladder, 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. Steel and aluminum rope ladders as sometimes used in vertical caving.
* 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 O / square>
* 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 Aluminum step ladder 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.
* Assault ladders. These are designed to be used by units which may need to board or assault vessels or buildings. They can be used when a full sized ladder is not required or when working in confined spaces. Suited for covert operations such as sniper placement, and vessel boardings. It was developed and designed for tubular assaults including buses and trains and for first story breaching. Its extra wide design gives the user greater stability, but still can fold away to be stored. It is available in standard Aluminum Ramp or non-reflective black finish in 6 and 8 foot lengths. from:http://zhongxinladder.blogtownhall.com/
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Aluminum, step, ladder,
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