Craftyquilter posted this url.
http://www.waukinvnetcorp.com/myquiltgenie/mgq_hst.php
I think the "magic" is to make your half square triangles from squares that are N and 7/8th inches. For example, 4 and 7/8th.
Do a search on half square triangles and pinwheels, too. Lots of info posted.