Question on the rulers, I have never done a BH mystery (although I have made several of her designs) I see a lot of you are buying the rulers or maybe have something usable. Those of you that already have them, do they save enough time & frustration to pay for them selves? Are they something I will use over again or possibly a one time thing? I haven't found them at LQS to look at them to see how they work. Any thoughts on these questions will be greatly appreciated. Thanks