Quilters Select Combo Triangle-Square Ruler
Your Ultimate Tool for cutting half-square & quarter-square Triangle units, plus basic squares up to 6 ½”!
Eliminate the tedious math associated with traditional half and quarter square triangle units.
Create complex looking blocks with ease thanks to the Unique Non-Slip Coating for accurate cutting!
Here's a link to their product page with "How-To's" and a free project! [scroll to the bottom] Ruler info and a free project.