This tool is a must have even if you're going to use once a year or in your lifetime. I havent used it yet for stair treads but mainly for shelves either for a single shelve for a closet or doing a full blown custom pantry shelves. the tool is super easy to use and can easily modify by screwing scrap of wood (has to be straight and with a slight bevel to it) through the holes. can do any variety of widths. widest shelve i done was 2 feet deep and makes it so precise and efficient.