Thanks for show us this ruler, I think I understand how it works..
Excellent. After reading the previous post, I went out looking. I found a formula that adds 7/8 inch to pretty much any size square to make the corresponding half square triangle. Maybe this is too simple? I also dug out my templates, I have a lot to learn.
that little 7/8 is what this ruler avoids. It does make the thinking before the cutting a lot more simple. Also the fact that you actually are sewing on a drawn line, instead of using your foot to gauge the 1/4", probably makes it a bit more accurate .