I do a lot of applique and having taken several courses from Karen (one being a Baltimore Album w/3-D flowers), this ruler would serve me best in squaring up once the applique was completed. She touched on the 3-D thing lightly in her demo, but what she was saying in using a conventional square ruler, it rocked over the 3-D and it was impossible to lay the ruler flat and get a good line for cutting and squaring. We students even attempted to make a frame to surround our work for a cutting guide. Squaring up was very difficult but I can see this ruler would be so helpful. This ruler may have to go on my Christmas wish list.
Incidentally, if you ever have the opportunity to take a class, a trunk show, etc w/Karen, please do so. She is obviously talented but also a "hoot and a hollar" (a fun fun teacher). When we took the Baltimore Album classes, she came to us every month for a year and we looked forward to her appearing and entertainment. AND, when you look at the video from #1 above, what you do not see in the yellow, rectangular quilt, that it is covered with beading. Just absolutely covered!! What a treasure!! -- Yep, I'm a Karen fan.