Thanks Syko for the clarification. my BUIS is a GG&G unit and is basically an A2 sight that has no elevation adjustment.
Teddy, the BUIS mounts on the back of the picatinny rail and folds down out of the way so i can mount whatever optic I want...in this case a 3-10X44 scope. if i have to remove the scope because of damage or low light or whatever, i simply flip up the BUIS and i'm ready to go. it's the setup i use for hogs because the scope gives me long range capability and with BUIS i have a good option if i'm in the brush.