The Johnson stud finder has a strong magnetic pointer to locate metal studs, as well as nails in wood. It also has a built-in level vial that's helpful when you're hanging mirrors and cupboards. The stud finder's reflective backing makes the level easier to see. A high-impact plastic base on the tool fits your hand for comfortable handling. Use this stud finder before starting carpentry projects destined for wall mounting. Hanging heavy items requires attaching them to the wall studs for safety.