Many rifle owners rely on a red dot or magnified optic as their primary sighting system. Optics are dependable, but batteries die, lenses get damaged, and mounts can come loose. Flip-up backup iron sights, often called BUIS, give you a simple mechanical fallback that stays out of the way until you need it.
A set of flip-up sights includes a front post and a rear aperture. In normal use, both fold flat so they sit low and do not clutter your view through the optic. If the optic fails, you press a button or lift the sight by hand and a spring locks it upright, giving you a usable sight picture right away.
Most backup sights clamp onto a standard Picatinny rail. The rear sight usually goes on the receiver rail behind the optic, and the front sight sits on the handguard or gas block rail. Tighten the clamps securely and check them periodically.
Iron sights are zeroed once at the range by adjusting windage and elevation until point of aim matches point of impact. After that, they generally hold their setting until moved.
With the sights raised, look through your optic to see whether the irons line up with the dot. This alignment, called co-witness, lets you confirm both systems agree. If you are shopping for a set, see these Ozark Armament flip up sights.