An arrow slit (often referred to more formally as an arrow loop) is a thin vertical aperture in a
fortification through which an
archer can launch
arrows largely free from personal danger.The interior walls behind an arrow slit are often cut away at an oblique angle so that the archer has a wide
field of view and
field of fire. This area in the thickness of the wall is also known as the
embrasure. Arrow slits come in a remarkable variety. A common and recognizable form is the
cross. The thin vertical aperture permits the archer large degrees of freedom to vary the
elevation and direction of his bowshot but makes it difficult for attackers to harm the archer since there is only a small target to aim at.
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The narrow opening in a
castle wall, a window, through which
archers could shoot but still have substantial cover. The inside of the opening was often tapered to allow the archer a larger field of fire.