Use an existing wall outlet that you are not using. A wall outlet that is used often isn't a suitable place to store valuables. Unscrew the faceplate and either use the existing compartment, or replace the compartment with a commercially available safe.
Find a place on your wall where an additional outlet would look natural. Use the stud finder or knock with your fist to be sure that the space is hollow and not backed by a stud.
Trace the outside of the switch box on the wall.
Use the rotary cutter to remove a section of drywall just larger than the switch box.
Cut off the top of the switch box with the rotary cutter, leaving the open front of the box untouched.
Attach the electrical socket to the open face of the switch box.
Screw the faceplate onto the electrical socket.
Place your valuables into the switch box, purchased safe or the original outlet compartment.
Screw the faceplate back onto the outlet if using an existing outlet.
Push a newly created decoy outlet into the opening you made in the wall until the faceplate is flush with the wall.
Buy a large hardcover book at a bookstore, library sale or find one at home that you don't mind ruining. Make sure the book is large enough that a safe with length and width 2 inches smaller and depth one-half-inch smaller will hold your valuables.
Open the front cover and the first few pages of the book. To keep the safe hidden it is better to leave a few loose pages in the front of the book.
Wrap these pages and the cover in plastic to protect it while cutting and gluing.
Separate the back cover and about one-quarter-inch to one-half-inch of pages from the middle pages.
Wrap these pages in plastic or cover them with the plastic bag.
Mark the outline of the safe you want. Leave one-half-inch to 1 inch on each side to maintain the secrecy and stability of the safe.
Use the utility knife, razor or saw to cut out the center of the remaining pages.
Remove a few back pages from the plastic wrapping.
Glue the inside pages together and glue them to the page(s) behind the "safe."
Glue a piece of felt or cloth to the inside of the safe if you want to have a cleaner more stable opening.