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.

We’ve all been there, right? “Oh, I just need to find a stud to hang a picture.” And 15 holes later, you’re convinced the wall is held up by pixie dust and a wish, because apparently there ...