Locate the studs on both sides of the applicable area using a stud finder. Use a pencil to mark their location and the location of the desired opening.
Place the point of the keyhole saw against the drywall in the desired location, and tap the handle with your hand to drive it into the drywall.
Cut the drywall by carefully sawing along the marked lines of the desired opening in short motions. Take your time and be cautious as electrical wires and plumbing pipes may run through the inside of the wall. For this reason, avoid using a reciprocating saw unless highly experienced in its operation. It is easier to detect a wire or pipe when cutting drywall using a keyhole saw. Remove the cut piece of drywall from the opening.