Applications
Perforation frequently refers to the practice of creating a long series of holes or slits so that paper or plastics can be torn more easily along a given line: this is used in easy-open packaging. Since the creation of perforation devices in the 1840s and 1850s, it has seen use in several areas. Postage stamps are one common application of this, where small round holes are cut in lines to create individual pieces (see postage stamp separation). Perforations on stamps are rather large, in the order of a millimeter, in comparison other perforated materials often have smaller holes. It is common for notebooks and legal pads to have perforations making it easier to tear out individual pages. In today's cases, perforation is used in ways to separate loose leaf (or even a form of graph paper from a ringed binder). A fine perforation next to the rings allows the page to be separated from the book with no confetti. Screwcaps on glass or plastic bottles are sealed with a ring at the bottom of the cap attached by perforation. Twisting the cap has the effect of rupturing the material between the perforations and indicating that the original seal has been broken.
Film stock is perforated to allow it to be moved precise distances at a time continuously. Similarly, punched cards for use in looms and later in computers input and output devices in some cases were perforated to ensure correct positioning of the card in the device, and to encode information.
Perforation of steel strips is used in the manufacture of some zesters and rasps.
Historically, perforation patterns other than linear were used to mark stamps (see Perfin). Today, similarly elaborate perforation patterns continue to be used in orienteering.
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