Mark Hidden Nailers With Post-It Notes
To mark the location of a stud or a hidden nailer, use a 3M Post-It Note or a similar adhesive-backed paper tab. These squares of paper can be left in place for days, they won't leave a pencil mark on your wall or project, and they won't peel up paint or finishes as masking tape might. What's more, you can draw level lines across the squares of paper to aid in the installation of shelves.
—Randy Lee, Fairfield, Ohio