Help Ruler

Rulers have long been made of wood in a wide range of sizes. Plastics have
been used since they were invented; they can be molded with length markings
instead of being scribed. Metal is used for more durable rulers for use in
the workshop; sometimes a metal edge is embedded into a wooden desk ruler
to preserve the edge when used for straight-line cutting. 12 inches or 30
cm  in length is useful for a ruler to be kept on a desk to help in
drawing. Shorter rulers are convenient for keeping in a pocket. Longer
rulers, e.g., 18 inches (45 cm) are necessary in some cases. Rigid wooden
or plastic yardsticks, 1 yard long and metre sticks, 1 metre long, are also

Desk rulers are used for three main purposes: to measure, to aid in drawing
straight lines and as a straight guide for cutting and scoring with a
blade. Practical rulers have distance markings along their edges.

A type of ruler used in the printing industry is called a line gauge.
These may be made from a variety of materials, typically metal or clear
plastic. Units of measurement on a basic line gauge usually include
inches, agate, picas and points. More detailed line gauges may contain
sample widths of lines, samples of common type in several point sizes, etc.

Measuring instruments similar in function to rulers are made portable by
folding (carpenter's folding rule) or retracting into a coil (metal tape
measure) when not in use. When extended for use they are straight, like a
ruler. For example, some 2-meter carpenter's rulers can fold down to a
length of 24 cm to easily fit in a pocket, and a 5-meter-long tape can 
retract into a small housing.

A flexible length measuring instrument which is not necessarily straight in
use is the tailor's fabric tape measure, a length of tape calibrated in
inches and centimetres. It is used to measure around a solid body, e.g., a 
person's waist measurement, as well as linear measurement, e.g., inside 
leg. It is rolled up when not in use, taking up little space.

A contraction rule is made having larger divisions than standard measures 
to allow for shrinkage of a metal casting. They may also be known as a 
'shrinkage or shrink rule.

Rulers made of Ivory were in use by the Indus Valley Civilization period
prior to 1500 BC. Excavations at Lothal (2400 BC) have yielded one such 
ruler calibrated to about 1/16th in (1.6mm).[3] Ian Whitelaw holds that
the Mohenjo-Daro  ruler is divided into units corresponding to 1.32 in
(33.5mm) and these are marked out in decimal subdivisions with amazing 
accuracy, to within 0.005 in (0.13mm). Ancient bricks found throughout 
the region have dimensions that correspond to these units.

Anton Ullrich invented the folding ruler in 1851.

Since it serves very little purpose to use metal, plastic, or wooden
rulers in the game, this command instead displays a text bar to measure
your screen's display width (up to 100 characters).