I did not see a one-use ruler, but I did see a 7" X 12" rectangular template with a cutting curve built in. I offered to help a friend cut for a group of children she was teaching to make quilts, thinking it would be 5, 6 or 6.5 inch squares. When she said 7" squares, I had to re-think how I would do it. Sometimes I can get off the mark when lining up fabric with a long ruler that is 8" or 6.5" wide.

I have used it to draft and modify traditional designs when making a pattern.

Check out Phillips Fiber Art - they are featuring this ruler today. They also offer a couple free patterns using this ruler

Yes, I have one and it works well. It comes with very good instructions. It does have a slot that you insert your rotary cutter.

At their site Cheryl has some free patterns that you can download using that ruler and some tutorials.

I made this quilt using the qcr and won best in show at a local challenge. It took some getting used to and I probably would have had an easier time if I'd bought a pattern. I just muddled through with the freebie directions on the web. [ATTACH=CONFIG]549410[/ATTACH][ATTACH=CONFIG]549410[/ATTACH]

You are thinking of a different ruler. The OP is asking about the Sew Kind of Wonderful Quick Curve Ruler. Phillips Fiber Arts does not sell it.
This is the ruler the OP was asking about
http://sewkindofwonderful.com/collections/all

There are many quilt shops that carry it but Phillips Fiber art is not one of them. They do have a curve ruler that looks very much like the same idea though.

I have this ruler and really like it. I am going to make more of their patterns, they are really quite easy and fun!

Thanks for the information about the longarm ruler. Hadn't seen that one yet.

I admit, I am a ruler and gadget junkie. I have the QCR and the longarm ruler that goes with it. Love them both. There is a learning curve, but once you watch the videos a few times, it isn't so hard to follow their patterns. The first quilt I made with the ruler I used my normal 45mm rotary cutter and it was okay but then I realized that a 28mm works much better on those curves. I'm working on my third Sewkindofwonderful pattern now, Metro Medallion. You can't speed through these patterns but I love a challenge.