[header] How to install a medicine cabinet [title] Scan the wall with a stud finder. [step] Use a stud finder to locate your wall's studs, and mark the locations of the studs with a pencil. Bathroom walls can conceal pipes and electrical wires, so you should use caution if your stud finder identifies any other objects behind the drywall. 
Drilling through pipes or wires can result in expensive damage. [substeps] If you are concerned about possible pipes or electrical wires, consult with a professional before you drill or cut into the wall.