I used this ruler for squaring up the half square triangle blocks. I bought the ruler in Kansas City this Spring at the Machine Quilters Show. The ruler is made by DbarJ Quilts etc. out of Rockville, MO and the website is dbarjquilts.com. This ruler can be used for 2.5, 3.5, 4.5, 6.5, and 8.5 inch squares. I really liked it.