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. A series of patents had been issued in the late 19th century for perforation machines to be used on rail lines for ticketing. Libraries and private collections used similar perforating stamps to mark ownership of books. End sheets, title pages, and image plates were punched with the namesake of the collection. Today, similarly elaborate perforation patterns continue to be used in orienteering. Bread bags for some bread often have micro-perforations in the plastic, which is supposed to keep the bread fresh by releasing excess moisture. Similarly, bags of concrete use small perforations to allow air to escape while they are being filled. See also
Film perforations
Punched tape


== References ==
While there is a general correlation between the size of units, the area within which they operate, and the scope of mission they perform, the correlation is not absolute. In fact, it is ultimately the mission that a unit performs that determines the level of war within which it operates. Operational level of war
The operational level of war occupies roughly the middle ground between the campaigns strategic focus and the tactics of an engagement. It describes "a distinct intermediate level of war between military strategy, governing war in general, and tactics, involving individual battles". For example, during World War II, the concept applied to use of Soviet Tank Armies. See also
Civil-military operations
Effects-Based Operations (EBO)
List of military operations
List of coalition military operations of the Iraq War
List of World War II military operations
Military operation plan
Military operations other than war (MOOTW)
Offensive (military)
Operational View (OV)

Notes
References
Armstrong, Richard N. Red Army Tank Commanders: The Armored Guards. Atglen, Penn. : Schiffer Military History, 1994. ISBN 0-88740-581-9. Glantz, David M. Soviet Military Operational Art: In Pursuit of Deep Battle. London: Frank Cass, 1991. ISBN 0-7146-3362-3, ISBN 0-7146-4077-8.