Q. I need to install shelves in various rooms. I was given a stud finder to help determine the best places to hang the shelves. For the life of me, I can’t figure out how to use it! Any advice? A.

If you’re hanging or mounting heavy items on your walls, such as mirrors or flat-screen TVs, you need to attach them to a stud—the wooden or metal beams that make up your home’s framing. Since these ...