It does not matter if you are trying to hang a book shelf, towel rack or TV. The only way to keep heavy items attached to your wall is to tie the item into a stud. A stud is a structural support for the wall. Basically studs are the bones of a building and can be made of wood or metal and are spaced 16 inches or 24 inches apart inside a wall.
There are 5 sure ways to find a stud inside a wall.
BASIC DETECTIVE WORK
Check the wall for nails or nail holes in moldings as these will be tied into studs. Electrical outlets are also usually tied to studs (stud is usually on the right hand side). Since most studs are 16 or 24 inches apart, you can get a good idea of the layout of the studs inside the wall by measuring out from a light switch or electrical box.
SHINE THE LIGHT
If there are no electrical boxes or receptacles on the wall, get a flashlight and shine the light at a flat angle along the wall. The light will reveal depressions and dimples where nails or screws are located. You might also bee able to find a seam where two pieces of drywall meet. These edges are always located on a stud.
My grandfather would use his knuckles and tap across the wall listening for a sound change. The sound is empty between studs and more solid over a stud.
The fastest way to find studs is by using an electronic stud finder. A stud finder is a small tool that measures changes in density. All you do is pass the stud finder over the wall and the stud finder will beep or show a light display that indicates when it finds a stud. For modern buildings, walls may be made of metal studs. To find these types of studs, use a magnetic stud finder. Just like the wood stud finder, just slide the tool over the wall until the magnetic bar highlights the stud. Magnetic stud finders also will detect pipes, and metal cable so you should exercise some caution.
DRILL AND SEARCH
Of course you could just drill a hole and if you don’t hit a stud, insert a stiff wire through the hole and feel for a stud. Many people will use coat hangers for this.
Once you’ve found a stud, measure out 16 inches (some building codes allow 24 inches).
Taking a few minutes at the beginning of your project to find the studs will ensure that you can hand your shelf, wall mounted TV or towel rack with confidence.