Buy a 2 oz bottle of Ruler Magic and get a 1/2 oz travel size free!
A few drops will hold your ruler in place after only 5 minutes!
This easy to use product goes on as a white liquid and dries clear in about 5 minutes. Any smooth surface becomes tacky and even your largest ruler or template will stay in place with very little effort.
Need to clean it? Simply rinse with cold water. Removable with hot water and/or a mild household cleaning spray. "Soak in hot water for abut 5 minutes, wipe off with a soft, abrasive sponge"