Safety first make sure the weapon is cleared twice "no ammo".
Locate screw on the lower portion of the front hand guard, remove screw, slide front hand guard off.
With the Chaos top rails separated from the bottom, slide the bottom rail rear key into the receiver and place the 5x12mm screw into the bottom rail and tighten (we recommend using blue Loc-tite on all mounting screws for this rail.
Place top rails on bottom rail and tighten 4 6-32 screws do not over tighten get good and snug.
If you have any problems please feel free to contact us 812-250-4919.