take a whole bunch of basses, put them ON TOP OF EACH OTHER(this is key). now make sure that you use an even number of basses(you'll see why in a moment). take the total number of basses you have in the pile, and divide by 2(no more, no less.... dividing by 4 is right out). take (off the top of the pile) exactly the number you came up with.... viola, a bass halfstack.