Been mounting keypads with the little bubble level taped to the wall for 6 months, way faster than marking and drilling | Alarm System Installers - nhfree.com
Did your friend ever tell you about the time he tried that trick on a brick wall? He taped the level to the keypad, got it all set, drilled the holes perfect, then the level fell off and landed right on his phone. Screen cracked, keypad was crooked, whole thing was a mess. He still swears by the tape method though, just uses way more tape now. I keep meaning to try it myself but I always forget to buy the little levels.