There are two types of ladders: rigid ladders that can be leaned against a vertical surface such as a wall, and rope ladders that are hung from the top. The steps of a ladder are called rungs, and the vertical members are called stiles. With a bit of agility, one can slide down the stiles without climbing down each rung. Rigid ladders are usually portable.
Rigid ladders are available in many forms, such as:
� fixed ladder (two stiles joined by several rungs; no moving parts)
� extension ladder (fixed ladder divided into two or more lengths for more convenient storage; the lengths can be slid together for storage or slid apart to maximize the length of the ladder)
� step ladder (hinged in the middle to form an upside down V)
� roof ladder (rigid ladder with large hook at the top to grip the ridge of a roof)
� hook ladder (rigid ladder with a hook at the top to grip a windowsill. This is the type used by firefighters)
Rigid ladders were originally made of wood, but in the 20th century aluminum became more common because it is ligher. Ladders with fiberglass stiles are used for working on electrical wires, because fibreglass is an electrical insulator and provides additional safety for the workers.
For proper use, a rigid ladder should be leaned at a fifteen degree angle. To put it simply, the foot of the ladder should be a quarter of the height of the ladder or less. At steeper angles, the ladder is at risk of falling backwards when the climber leans away too far. 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.
Rope ladders are used where storage space is extremely limited, or weight must be kept to a minimum. 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. These are often seen on obstacle courses, or with military equipment, and are far less common than ridge ladders because ridge ladders have many more obvious and useful applications.
Common, useful tools, ladderss serve the most basic of functions yet certain aspects of home improvement would be impossible without them. It's amazing to think how difficult many aspects of life would be without such a basic advancement.
Dave is the owner of http://step-ladders.info and http://extension-ladders.info websites providing information on ladders
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