Gonna buy me some clear medical tape....thanks ladies!

I was given the Invisi Grip by Omnigrid and it seems to work fine with my older rulers. Before I used the sandpaper circles and the rubber circles but they both fell off in time. Using the Invisi Grip is saving me from having to replace my rulers sooner than I want to.

3M Safety Walk Slip resistant tape (clear) Found it mentioned on this Board. It was not easy to find. Home Depot website said it was at 2 of my local stores. Was Not. Got it from Amazon. Little Pricy but it works. You do not need big pieces on the rulers - I cut 1/4" wide pieces. It was suggested that you use a utility scissors and keep it for this application only. I got scissors from the Dollar Store - worked great. It is basically cut, peel of backing, stick on back of ruler.

This is going to sound like an infomercial, but -- Clear Flex-Seal. Yes, that spray-on rubber stuff that you've seen ads for a bazillion times. Make sure it's the clear and not the opaque variety! Just give your rulers a light misting on the back and let them dry. It does give them a bit of a frosty look, but nothing that interferes with using the ruler. I have tried invisigrip, sandpaper dots, tape, rubber cement, but nothing else works as well as the Flex-Seal.

try clear plastic wrap it does not slip and you probably already have it on hand, read it here or in a magazine

shelf liner is the way to go
 

I keep a whole roll near by as I am always losing the square, or cutting it in half. I also give them away to my quilting friends.