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    (Wikipedia) - Ladder For other uses, see Ladder (disambiguation). "Step ladder" redirects here. For the EP by Teddy Geiger, see Step Ladder (EP).
    This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (May 2007)
    An extension ladderA ladder used for ceremonial purposes in Indonesia

    A ladder is a vertical or inclined set of rungs or steps. There are two types: rigid ladders that can be leaned against a vertical surface such as a wall, and rope ladders that are hung from the top. The vertical members of a rigid ladder are called stringers or rails (US) or stiles (UK). Rigid ladders are usually portable, but some types are permanently fixed to buildings. They are commonly made of metal, wood, or fibreglass, but they have been known to be made of tough plastic.

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    Variations

    Rigid ladders are available in many forms, such as:

    Rigid ladders were originally made of wood, but in the 20th century aluminium became more common because of its lighter weight.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. Henry Quackenbush patented the extension ladder in 1867.

    SafetySafe setup of a leaning ladderSkid mark from a faulty ladder.

    The most common injury made by ladder climbers is bruising from falling off a ladder, but bone fractures are common and head injuries are also likely, depending on the nature of the accident. Ladders can slip backwards owing to faulty base pads which usually fit into the ladder stiles. If badly worn, they can allow the aluminium to contact the ground rather than plastic or rubber, and so lower the friction with the ground. Ladder stabilizers are available that increase the ladder''s grip on the ground. One of the first ladder stabilizers or ladder feet was offered in 1936 and today they are standard equipment on most large ladders.

    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.

    It has become increasingly common to provide anchor points on buildings to which the top rung of an extension ladder can be attached, especially for activities like window cleaning, especially if a fellow worker is not available for "footing" the ladder. Footing occurs when another worker stands on the lowest rung and so provides much greater stability to the ladder when being used. The anchor point is usually a ring cemented into a slot in the brick wall to which the rungs of a ladder can be attached using rope for example, or a carabiner.

    If a leaning ladder is placed at the wrong angle, the risk of a fall is greatly increased. The safest angle for a ladder is 75.5°; if it is too shallow, the bottom of the ladder is at risk of sliding, and if it is too steep, the ladder may fall backwards. Both scenarios can cause significant injury, and are especially important in industries like construction, which require heavy use of ladders.

    Ladder classes

    The European Union and the United Kingdom established a ladder certification system – ladder classes, for any ladders manufactured or sold in Europe. The certification classes solely apply to ladders that are portable such as stepladders and extension ladders and are broken down into three types of certification. Each ladder certification is colour-coded to indicate the amount of weight the ladder is designed to hold, the certification class and its use. The color can be found on the rubber feet of each ladder and on the certification symbol.

    In the UK there are a number of British standards included in the three main ladder certifications relative to the particular ladder type. Relevant classifications include BS 1129:1990 (British) which applies to Timber Ladders and Steps; BS 2037:1994 (British) which applies to Metal and Aluminium Ladders and Steps and BS EN 131:1993 (European) which applies to both Timber and Aluminium Ladders and Steps.

    Uses Historical usageOn the right hand page are types of ladders from the end of the 15th century in Germany.

    Ladders are ancient tools and technology. A ladder is depicted in a Mesolithic rock painting that is at least 10,000 years old, depicted in the Spider Caves in Valencia, Spain. The painting depicts two humans using a ladder to reach a wild honeybee nest to harvest honey. The ladder is depicted as long and flexible, possibly made out of some kind of grass.

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