TYPES AND USES
The rule or tape is used for measuring where accuracy
is not an extremely critical factor. They can be rigid or
flexible, come in various lengths, and can be made of
wood, metal, cloth, or fiberglass.
The rule is the most common of measuring tools. This
rule is usually 6 or 12 inches in length, although other
lengths are available. Steel rules may be flexible or
nonflexible, but the thinner the rule, the easier it is to
measure accurately because the division marks are
closer to the work.
A rule usually has four sets of graduations, one on each
edge of each side. The longest lines represent the inch
marks. On one edge each inch is divided into 8 equal
spaces so each space represents 1/8 in. The other edge
of this side is divided in sixteenths. The 1/4-in. and 1/2-
in. marks are commonly made longer than the smaller
division marks to facilitate counting, but the graduations
are usually not numbered individually, as they are
sufficiently far apart to be counted without difficulty.
The opposite side is similarly divided into 32 and 64
spaces per inch, and it is common practice to number
every fourth division for easier reading.
There are many variations of the common rule.
Sometimes the graduations are on one side only,
sometimes a set of graduations is added across one end
for measuring in narrow spaces, and sometimes only the
first inch is divided into 64ths, with the remaining inches
divided into 32nds and 16ths. A metal or wood folding
rule may be used.
These folding rules are usually from two to six feet long.
The folding rules cannot be relied on for extremely
accurate measurements because a certain amount of
play develops at the joints after continued use.
Steel tapes are made from 6 to about 300 feet in length.
The shorter tapes are made with a curved, but rigid,
cross section flexible enough to be rolled up. Long, flat
tapes need support over their full length to avoid
sagging. Lack of support can cause reading errors. The
most common types of steel tapes have a hook at one
end to let one person take all the readings.