My Rule Steady from Australia has the balls on the bottom. I bought it years ago. It holds the ruler down tight on the fabric just as it does on fabric only. It saves me time just using it on top of the ruler. The couple in Paducah did develop it to market as holding the fabric not the ruler. I have their version also. I use theirs on top of my ruler too. To each her own but try it on top of the ruler before saying it won't work.