A Crémaillère is a French, mechanical term for the rack, or a straight bar with teeth on one edge designed to work into the teeth of a wheel or a pinion (French pignon) that predates the Renaissance. The term was generally applied in English to engineering applications which had notched, toothed or drilled surface, even when only visually so, such as the edge of the staircase. The term is also applied to the rack railway

Rack railway

A rack-and-pinion railway is a railway with a toothed rack rail, usually between the running rails. The trains are fitted with one or more cog wheels or pinions that mesh with this rack rail...

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During the 17th to 19th centuries the term was widely applied to lines of entrenchment that are usually formed in a saw-tooth pattern, known as indented lines, particularly during siege

Siege

A siege is a military blockade of a city or fortress with the intent of conquering by attrition or assault. The term derives from sedere, Latin for "to sit". Generally speaking, siege warfare is a form of constant, low intensity conflict characterized by one party holding a strong, static...

s. These lines are usually employed on banks of rivers, or on ground which is more elevated than, or which commands, that of the enemy. The defence of these lines is sometimes strengthened by double redan

Redan

Redan is a term related to fortifications. It is a work in a V-shaped salient angle toward an expected attack...

s, and flat bastion

Bastion

A bastion, or a bulwark, is a structure projecting outward from the main enclosure of a fortification, situated in both corners of a straight wall , facilitating active defence against assaulting troops...

s constructed at intervals, along their front. Just such a constructed defence was used at Centreville

Centreville, Virginia

Centreville is an unincorporated community in Fairfax County, Virginia, United States. Recognized by the U.S. Census Bureau as a Census Designated Place , the community population was 71,135 as of the 2010 census and is approximately west of Washington, DC.-Colonial Period:Beginning in the 1760s,...

 in 1862 during the American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

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The term is also applied in Artillery

Artillery

Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...

 to refer to an indented battery, or à Crémaillère constructed with salient and re-entering angles for obtaining an oblique, as well as a direct fire

Direct fire

Direct fire refers to the launching of a projectile directly at a target on a relatively flat trajectory. The firing weapon must have a sighting device and an unobstructed line of sight to the target, which means no objects or friendly units can be between it and the target...

, and to afford shelter form an enfilade fire of the enemy.