Square in a Square Rulers/Tools - we recommend to start with the Original Ruler.  It comes with a great Quick & Easy pattern book to help you get started with the Square in a Square technique.  As a second item to get, our Reference Book Vol 1 is the main book for the system.  Once you have this book, you have lots of ready to go patterns plus you can adapt other patterns to the easy Square in a Square method.

Quick Video on the products -