I use templates with my long arm and this tip pertains to that, but it could also be used for rotary rulers and templates as well. This tip was shared with me by Deb over at Quilts N Things Done by Betty Boop.
Here is a border on a quilt I recently quilted. I used a swag template made by Handi Quilter to achieve this design.
Most of my long arm rulers I want to slide over my quilt top. But some templates I want to stay in a very specific spot, so they need a little griping help. For that, I use a little Mob Grip. This product is designed for use on skateboards.