The KeyMod specifications call out a 'recoil lug' on the accessories which is intended to interface with the larger through hole portion and resist slippage of accessories during counter-recoil. The spacing of the holes is critical and is based on MIL-STD-1913 spacing to allow the greatest modularity with existing accessories. This prevents loss of small parts (screws, nuts or other small parts used in the assembly of the accessory). In most accessories, the screw is swaged after assembly to ensure that it cannot be backed out of the nut. This eliminates the need to align the nuts to the holes prior to accessory installation as well as the need for tools to tighten the screw/nut. The full diameter is left intact to create two flats on the nut which align the nut to the slot, and allow it to be indexed to the accessory as well as to the KeyMod slot. The angled face created is meant to interface with the chamfer on the backside of the KeyMod slot. The nut is stepped and the larger diameter end is chamfered around 270 degrees of its diameter. The slot is chamfered on the backside while the through hole is sized for clearance of a quick-detach sling swivel (approximately 3/8' diameter). The slot is distinctive with a larger diameter through-hole combined with a narrow slot. The KeyMod system consists of two parts: the KeyMod slot and the KeyMod nut. The KeyMod system allows a user to place MIL-STD-1913 rails wherever needed (even in the 45° positions at times). The goal is to eliminate the need for the rail to be fully outfitted with 1913 rails covering the entire handguard. The KeyMod system is intended to be used as a direct attachment method for firearm accessories such as flash light mounts, laser modules, sights, scope mounts, vertical grips, rail panels, hand stops, barricade supports, and many others.

KeyMod is an open-source design released for use and distribution in the public domain in an effort to standardize universal attachment systems in the firearm accessories market. The name 'KeyMod' was coined by Eric Kincel (then working for VLTOR Weapon Systems) following the naming trend of other VLTOR accessories with the suffix 'Mod' meaning modular, and 'Key' being a reference to the key-hole profile of the mounting slots. The concept was first created by VLTOR Weapon Systems of Tucson, Arizona, and released through Noveske Rifleworks of Grants Pass, Oregon, before being published open sourced in the public domain for adoption by the entire firearms accessory industry. KeyMod is a universal interface system for firearm accessory components designed to supersede the MIL-STD-1913 accessory rails.

Keymod accessories install