I walked into a class last week with all of my pieces cut up, ready to sew. I informed the instructor that I did not want to draw lines on the back of my little squares in preparation for making my 160 flying geese blocks. I don't want to draw the lines, I don't like drawing the lines, etc.
As I was preparing to figure out how to lay tape on my machine so I'd have a straight edge to run the corner of my little sqaure along as I sewed it to the rectangle, the instructor suggested this tool. It was relatively short money and will do more than just one thing so I did purchase it with my class discount.
I have to say that I've never had an easier time getting those little squares sewn on so they fold over near-perfectly. Usually, I'm resewing many of them. I only had to resew a half-dozen or so.
It's called the Angler 2.