Thanks for responding Old/New but the tool is the problem. I have a drywall saw the works well for complex shapes. The problem is how can I trace the complex outline of the back of a round fixture box onto the drywall? Lacking better suggestions, my plan is to cut a circle slightly larger than the box inside diameter, set the box in as far as it will go, mark whatever protrusion is hitting, remove the box and cut that small bit out, then repeat that process until it is all the way in. I am hoping that someone has a more elegant alternative to that brute force approach. I am surprised the manufacturer does not provide a template to go with the box.