I swiped some of hubbies sand paper. I cut little squares off of it and stuck them on almost all of my rulers. The bigger ones have more dots than the smaller ones. I try to keep them out of the way of measure marks that I use a lot though.
I've taken the narrow strips of double sided tape from my scrapbook supplies for my smaller rulers. My only advice on that one is to leave a little hangy piece at the end to pull it back up with when it needs replaced. I only use this on the short ruler types though.
I've heard you can make your own dots with a hot glue gun. You just put little dollops on, let them dry and that's that. They should pop right off too when you want to replace or move them.