KeyMod

KeyMod is a modular rail system standard developed for firearms, designed as a direct competitor to the Picatinny rail system and its subsequent derivatives. It allows for the direct attachment of accessories such as grips, lights, lasers, and sling mounts to a firearm's handguard or forend without requiring the use of Picatinny rail sections as an intermediary.

The KeyMod system utilizes a series of keyhole-shaped slots arranged in a specific pattern. Accessories equipped with KeyMod hardware attach directly to these slots by inserting T-shaped nuts through the larger circular portion of the keyhole and then sliding them forward into the narrower slot to lock the accessory in place.

The primary advantage of KeyMod is its reduced weight and slimmer profile compared to Picatinny rails. By eliminating the need for full-length rails and allowing for accessory attachment only where needed, KeyMod systems can significantly decrease the overall weight of the firearm and improve ergonomics. Another purported advantage is improved comfort and grip, as the absence of raised rails provides a smoother surface for the user's hand.

The KeyMod system was developed and released into the public domain by VLTOR Weapon Systems and Noveske Rifleworks in 2012. While initially gaining considerable traction within the firearms industry, its popularity has waned in recent years due to competition from other modular rail systems, most notably M-LOK (Modular Lock). The M-LOK system, developed by Magpul Industries, offers a similar modularity and lightweight design and has achieved wider adoption due to various factors including industry testing and licensing agreements. Despite this, KeyMod remains a viable option and is still found on some firearms and accessories.