The term iron sights refers to the open, unmagnifie system used to assist the aiming of a variety of devices, usually those intended to launch projectiles, such as firearms, airguns, and crossbows; they are also used on many telescopes to help point the telescope at a desired target. Iron sights usually consist of some form of notch or aperture in the rear sight and a post, bead or ring in the front sight. Often, the rear sight is adjustable for windage and/or elevation, though in many military rifles, the front sight is also adjustable.