The rail have the protrusions that lock into the Key Mod holes. Solidly attached using the key mod rail interface, for rifles, shotguns paintball & airsoft; Excellent System: Fits to attach for Gun/Rilfe Tactical Accessories on airsoft rifles. Lightweight and durable: Made of premium Aluminum Alloy, without any load on the rifle. Ideal for tactical flashlight, laser, optics, bipods, and grips; 4 x Screw , 4 x Nut , A Allen Wrench to Lock Rails.