I use a thin coat of old fashion Rubber Cement on the few rulers that are super slippery (most of those rulers are my long arm rulers). I apply it and let it sit for a while, it dries clear, it is super non-slide and when it looks nasty with threads, rubs off cleanly for a fresh coat. The only problem is that I used to be able to purchase anywhere but the last time all I could find were small containers in local store and ended up purchasing off of Amazon,