I have 2 speed squares. A 6" and 12". A lot of guys, myself included, use it as a guide for a circ saw to cut 90 degrees on dimensional lumber. However, when i bought mine (at Home Depot) it came with a pretty thick and informative manual explaining how to use it and all of its cool functions. Of course, i put it in the "file" with my VCR instruction manual. Funny, the dang thing still flashes 12:00. Hope this helps

Dave

just check around at stores where speed squares area sold...most places also sell the little guide book for a buck or two...its a good guide

Check out one of the competitors websites...
http://www.thisoldhouse.com/toh/

This months issue of the magazine has a good article about squares, including the speed square. And the article is at the website.