The point I was making was that your rifle doesn't have to be level and you don't have to use a plumb string or anything else if you use a collimator. Once you put the spud in the barrel, the vertical lines will be in line and once you line up the vertical lines with the crosshair point and align the vertical line you coincide with and the vertical cross hair line, everything should be square to the rifle bore, scope bore, and mounts as long as your mounting screws/bases are drilled straight in line with the bore... am I missing something?