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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 ...
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.
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 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 surveyor's tripod with a shoulder strap. The head of the tripod supports the instrument while the feet are spiked to anchor the tripod to the ground. A surveyor's tripod is a device used to support any one of a number of surveying instruments, such as theodolites, total stations, levels or transits.
The M192 Lightweight Ground Mount is a tripod fielded by the United States armed forces. It was designed and developed by Capco, Incorporated under contract through Picatinny Arsenal to replace the M122 tripod. [1] The United States Army named the tripod one of 2005's top ten inventions. [1] It was designed for use with the M249, M240B, and M240L.
The most widely known edition of snakes and ladders in the United States is Chutes and Ladders, released by Milton Bradley in 1943. [14] The playground setting replaced the snakes, which were thought to be disliked by children at the time. [14] It is played on a 10x10 board, and players advance their pieces according to a spinner rather than a die.
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 ...