Acrylic quilting rulers are very smooth. That’s good for a lot of things, but it makes it easy for the ruler to slip when you're cutting resulting in an inaccurate cut, or worse, injuring yourself. Giving your ruler some grip can help immensely with this so you don't have to apply a death grip to your ruler just to make a good cut.
There are a number of products out there designed to help with this. Check out this post for more information on other products and tips for making accurate cuts. I like to use clear window sticker vinyl sheets to make my rulers grippy. There are rolled vinyls, but they tend to be harder to apply. Here's how I apply vinyl to my rulers.
What you'll need:
First, lay the window sticker vinyl paper backing side up on your work surface. Place your ruler right side up on top of it positing the area you want to cover over the vinyl. I aim to cut my vinyl about 1/8" smaller than the ruler I want to cover so I don't end up with my vinyl coming off the edge.
NOTE: this isn't really all that important for the rectangular ruler I'm demoing this with right now, but for some more irregular rulers, you end up with mirrored pieces if you do this as described. (I've wasted more vinyl than I care to admit making that mistake!)
Next, take a pen or pencil and mark where you want to cut. Cut along that line or slightly inside of it, again, because I want my vinyl piece to be just slightly smaller than my ruler.
Peel the vinyl off the paper backing, flip the ruler over and position the vinyl where you want it, but not pressing yet.
Take a credit card or similar and firmly press the vinyl down squeegeeing out the air bubble working from the center out until the vinyl is well adhered.
Repeat this process with additional vinyl sheets until your entire ruler is covered. The drawback to using sheets is that you likely won't have a single piece to cover the whole ruler, but this is a minor concern in my opinion, compared with fighting a rolled vinyl that doesn't want to stay flat.
Once applied, leave it on the ruler until it comes off. You have grippy rulers for years.