Magpul chose not to open-source its creation, opting for free licensing instead. In 2014, Magpul upgraded the MOE style, debuting M-LOK which offered a similar look and feel to MOE, but with larger, durable, squared-sided slots. Continuing mounting innovation into 2009, the company released MOE handguards, bringing the same slot system to mainstream consumers.

The slot-like design originated in 2007 on the Masada Concept Rifle, which featured a polymer handguard with three vent holes acting as negative space for accessory mounting. Magpul’s Masada Concept Rifle was the first to feature slotted ports for accessory mounting. This design allows M-LOK compatible accessories to mount at the front or rear of the slots. The Modular Lock, or M-LOK, system ditches the keyhole shape in favor of slots and benefits from attachment lugs on accessories that are t-shaped and bi-directional. The open source nature encourages gear makers to use the lightweight system when designing handguards, accessories and even full rifles. The open source designation allows any company to make rails or accessories using KeyMod without paying royalties. The result of a partnership between VLTOR and Noveske, the open-source KeyMod design was released to the public domain in 2012. To attach an accessory, users line up the lugs on the part with the round part of the keyhole then slide it forward and tighten the screws.

KeyMod rails consist of rows of keyhole shapes that allow KeyMod-compatible accessories to mount into place on the handguard. KeyMod utilizes keyhole shapes to mount rifle accessories to the handguard.

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