How To Hang a Picture Ledge without Drilling Holes? -- Good Questions

Q: In the January Cure I decided the design element I really wanted to work on was a picture display shelf. But I live in a rental that doesn't allow drilling. Is there some combination of Command hooks, Monkey Hooks, and IKEA products that would allow me to hang a shelf with minimal patching required on the other end? I don't have a photo of my currently blank wall, but what I'd love to do is something like the photo shown here: