A tape measure or measuring tape is a flexible form of ruler. It consists of a ribbon of cloth, plastic,fiber glass, or metal with linear-measure markings, often in both imperial and metric units. Surveyors use tape measures in lengths on the order of hectometres. It is a common measuring tool. Its flexibility allows for a measure of great length to be easily carried in pocket or toolkit and permits one to measure around curves or corners.
Tape measures intended for use in tailoring or dressmaking were historically made from a flexible cloth or plastic. Today, measuring tapes made for sewing are made of fiberglass, which will not tear or stretch.(Readers Digest 10) Measuring tapes designed for carpentry or construction often use a stiff, curved metallic ribbon that can remain stiff and straight when extended, but retracts into a coil for convenient storage. This type of tape measure will have a floating tang on the end to aid measuring. The tang will float a distance equal to its thickness, to provide both inside and outside measurements that are accurate. A tape measure of 25 or even 1000 feet can wind into a relatively small container.
One little-known feature on most tape measures is a small black diamond that appears every 19.2 inches, known as the 'black truss' markings. This is used to mark out an equal five trusses per standard eight-foot sheet of building material.
The design on which most modern spring tape measures are built was patented by New Haven, Connecticut resident Alvin J. Fellows on 14 July 1868. According to the text of his patent, Fellows' tape measure was only an improvement on other versions previously designed.
The spring tape measure has been extant since Fellows' patent, but did not come into wide usage until the early 1940s, when it slowly began to supplant the folding wood carpenter's ruler. Today it is ubiquitous, even appearing in miniature form as a keychain fob, or novelty item.
Metal retractable tape measures are virtually maintenance-free. To extend their life, keep the measurement blade clean and don't retract the blade into the case too fast.
Readers Digest, The Complete Guide to Sewing Readers Digest Association,1995 ISBN0-88850-247-8