got a private label nxt thats almost finished

but have a question/problem...
nxt's have rails built into the frame but where is the tightening/adjusting screw for it??? I currently have a cp rail and dm on/off. id like to drop the rail and go straight with the on/off but its too loose and i dont see the adjusting screw...i believe stock nxt's have one inside the bottom of the grip frame but since this is a private label nxt i figured it has to be different.
any help would be appreciated! by dropping the rail i can lose some weight for it. if i gotta use a rail i gotta use a rail but i figure its there for a reason and im missing something lol. maybe its the manual.
