The square on the right is what you get when cutting a triangle from a "tube" when you are making a tube-quilt.
See the following links:
http://www.youtube.com/watch?v=vOWSp0mTTqE
The above link is neat and easy to follow. HOWEVER, She tells you to cut the third strip 4 inches wide. This is wrong.
http://www.quiltingboard.com/links-r...be-t99597.html