If I had any questions on how to use the framing square, first I would read a book on it. For about two dollars you can get a book down at most home centers (home depot, homeclub,acehardware). My favorite would be "The Little BLUE BOOK" by SWANSON'S. Same people who make the Speed Square. Next would be a book that used to come with the Stanley Framing square. Go to altavista.com and enter rafter square, there's a video you can order which explains how to use a Speed Square.