Rail integration system

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A rail integration system (RIS; also called a rail accessory system (RAS), rail interface system, rail system, mount, base, gun rail, or simply a rail^[1]) is a generic term for any standardized attachment system for mounting firearm accessories via bar-like straight brackets (i.e. "rails") often with regularly spaced slots.

Rail systems are usually made of strips of metal or polymer screw-fastened onto the gun's receiver, handguard, or fore-end stock to allow variable-position attachments. An advantage of the multiple rail slots is the moveable positions to adjust for optimal placement of each item for a user's preferences, along with the ability to switch different items at different placements due to varying eye reliefs on gun sights. Firearm accessories commonly compatible with or intended for rail systems include tactical lights, laser sights, vertical forward grips, telescopic sights, holographic sights, reflex sights, backup iron sights, bipods/tripods, slings, and bayonets.

The common types of rail systems for firearms are the dovetail rail^[2][3] (including the Soviet variant known as the Warsaw Pact rail), the Weaver rail,^[4] the Picatinny rail, the SOPMOD, the KeyMod and the M-LOK.^[5][6][7][8] There are also various non-military designs used in shooting sports to attach slings and bipods such as the UIT rail, Zeiss rail and Freeland rail.