Safety first make sure the weapon is cleared twice "no ammo".
Remove your front sight by turning it on it's side and taking a screwdriver placed against the side of the front sight tap it out, doesn't matter which side you tap it, it will remove for either side.
Once front sight is removed locate screw on the lower portion of the front hand guard, remove screw, slide front hand guard off.
With the Chaos rail top 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 rail on bottom rail and tighten 4 6-32 screws do not over tighten get good and snug.
It's not needed but you can remove the rear sight on the DDI 12 by unscrewing it from the rear dust cover.
The dust cover can be a bit difficult to remove and install with the rail installed, it is doable but will take some practice.
If you have any problems please feel free to contact us 812-250-4919.