I'm in the processes of making a scrappy one using the ruler and book from Gyleen Fitzgerald. You can get her ruler and book from her website
http://www.colourfulstitches.com/index.html She was an engineer for the government and designed this ruler, then wrote the book and gives classes. The ruler is very easy to use. Took a class from her a couple years ago. I just don't work on the blocks very often.