For those of you interested in the
BLOC LOC Ruler, here is a link. This is a great squaring ruler. There is a diagonal groove in it that locks right against the seam and you slide the ruler along the seam till you get to the size block you want to cut and them just trim the excess fabric away. I mainly work only with my standard rulers and not any special ones until I discovered this one. The HSTs are perfect, perfect and perfect. It is a little expensive. mine was about $22.00. I took a chance buying it and am glad I did.
Take a look!
I forget if mine is 6" or 6 1/2". And it cuts several sizes. There are many to chose from and I want to say I am not in any way part of this company. Just a good tool!
http://blocloc.com/
peace