http://www.quilterscache.com/T/Tilti...atchBlock.html
you mainly just need to be sure to leave 1/4 inch around your block when placing your ruler. that way you don't chop off points.
i took a class and we added rectangle strips and then trimmed with our ruler to tilt some left and some right.
http://smg.photobucket.com/albums/v6...rrent=1848.jpg
and
http://smg.photobucket.com/albums/v6...rrent=882f.jpg
some patterns call for those rectangles to be cut and then sewn on. less waste but i used what i cut off later on. no waste in my sewing room.