Aperture Sight

[′ap·ə‚chər ‚sīt]

An irregularly shaped adjustable mechanical item usually integral to a rear sight; it functions as a peephole through which the sight at the opposite end of a gun is brought into view in aiming at a target or object. An iron sight system of aligned markers used to assist in the aiming of a device such as a firearm, crossbow, or telescope that excludes the use of optics as in a scope. Also known as Peep Sights.

Aperture Sight
Aperture Sight