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John H. Balsley (May 29, 1823 – March 12, 1895) was a master carpenter and inventor, inventing a practical folding wooden stepladder and receiving the first U.S. patent issued for a safety stepladder in the year. He was born in Connellsville, Fayette County, Pennsylvania to George H. and Sarah (Shallenberger) Balsley. His father was also a ...
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.
The ladders are made by threading and fixing a series of hardwood, machined steps, each not more than 400 mm × 115 mm × 25 mm (15.75 in × 4.53 in × 0.98 in), onto two pairs of minimum 18 mm (0.71 in) diameter manila ropes, and binding each step to the ropes at 310 mm (12 in) (+- 5 mm, 0.20 in) intervals.
A pilot ladder has specific regulations on step size, spacing and the use of spreaders. 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.
Fall protection system: Fixed ladders above 24' must have a fall protection system in accordance with OSHA Standard 1910.28(b)(9)(i)(C). Cages are not anymore considered as fall protection, and ladders that are newly installed or replaced after November 19, 2018, must have a fall protection system based on OSHA's new fixed ladder requirements.
The initial setting operation includes fixing the theodolite on a tripod, along with approximate levelling and centering over the station mark.For setting up the instrument, the tripod is placed over the station with its legs widely spread so that the centre of the tripod head lies above the station point and its head approximately level (by eye estimation).
A tripod is a portable three-legged frame or stand, used as a platform for supporting the weight and maintaining the stability of some other object. The three-legged (triangular stance) design provides good stability against gravitational loads as well as horizontal shear forces , and better leverage for resisting tipping over due to lateral ...
Laboratory Tripod. A laboratory tripod is a three-legged platform used to support flasks and beakers. Tripods are usually made of stainless steel or aluminium and made light-weight for efficient portability within the lab. Often a wire gauze is placed on top of the tripod to provide a flat