I came across an advert for this the other day Parrs Reel Ruler, what a great invention for quilters.
This is ruler number 9, you need a starter kit that is £49.95 you get a non slip mat ruler number 1 which is a straight line and a special little foot for your sewing machine, the ruler is for free motion quilting, each ruler has a groove cut in it that guides the foot there is some great videos showing you how it works
here is a video of number 8
I got a selection of different ones and they are brilliant very easy to use, after you have the starter kit its £12 for each additional ruler, I believe they have 12 different designs available and have some new ones coming out soon.
I will do some top stitching in the next few days to show you after I have had a bit more practise.