505 is the best basting spray for quilts, but I would never try to use it on the backs of rulers. The grip strips from guidelines4quiltings are the BEST thing I have ever tried for rulers (and believe me, I've tried a lot of them). If you purchase, buy at least 2 packages because you are going to want them on every ruler you own (and the June Tailor Shape Cut mat, if you have one). Here is a link to the site that sells the grip strips:
http://www.guidelines4quilting.com/