TM 9-243TYPES AND USESThe rule or tape is used for measuring where accuracy isnot an extremely critical factor. They can be rigid orflexible, come in various lengths, and can be made ofwood, metal, cloth, or fiberglass.RULESThe rule is the most common of measuring tools. Thisrule is usually 6 or 12 inches in length, although otherlengths are available. Steel rules may be flexible ornonflexible, but the thinner the rule, the easier it is tomeasure accurately because the division marks arecloser to the work.A rule usually has four sets of graduations, one on eachedge of each side. The longest lines represent the inchmarks. On one edge each inch is divided into 8 equalspaces so each space represents 1/8 in. The other edgeof this side is divided in sixteenths. The 1/4-in. and1/2-in. marks are commonly made longer than thesmaller division marks to facilitate counting, but thegraduations are usually not numbered individually, asthey are sufficiently far apart to be counted withoutdifficulty. The opposite side is similarly divided into 32and 64 spaces per inch, and it is common practice tonumber every fourth division for easier reading.There are many variations of the common rule. Some-Steel tapes are made from 6 to about 300 feet in length..times the graduations are on one side only, sometimes aThe shorter tapes are made with a curved, but rigid,set of graduations is added across one end for measur-ing in narrow spaces, and sometimes only the first inchcross section flexible enough to be rolled up. Long, flatis divided into 64ths, with the remaining inches dividedtapes need support over their full length to avoid sag-into 32nds and 16ths. A metal or wood folding rule mayging. Lack of support can cause reading errors. Themost common types of steel tapes have a hook at onebe used.end to let one person take all the readings.FOLDING RULESThese folding rules are usually from two to six feet long.The folding rules cannot be relied on for extremely accu-rate measurements because a certain amount of playdevelops at the joints after continued use.STEEL TAPES8 - 2
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