Where do I set snap distance? for instance i would like to set snap to 6" in both planes AND my grid to 6" so that my snap is easier to see? I am doing simple house plans with mouse. Getting it to land on 4' is next to impossible, i.e., I get 4' 1/4" or 3' 11-3/4" manually. I've been entering the dimension I want in the box which is tedious.