Place the sensor vertically against the wall in a spot you believe does not have a stud. Press and hold the button on the side of the sensor. Wait for the top light to appear and disappear on the sensor. This signals it has calibrated.
Continue holding the button on the side of the sensor and pressing the sensor against the wall. Slide the sensor horizontally across the wall. The row of lights will begin to illuminate as the sensor approaches a stud.
Stop and hold the sensor in place on the spot at which all of the lights are illuminated. This signals the location of a stud. Use the pencil to mark this location on the wall.
Continue sliding the sensor along the wall. Stop on the point at which the top light turns off. This is the end of the stud. Mark this point with the pencil. The space between the first and second markings is the location of one stud.
Hold the stud finder against the wall, 2 inches from the floor. Slowly slide it horizontally across the wall.
Watch the stud finder as you move it across the wall. Stop on the point at which the needle stands perfectly erect. This marks the location of a stud. Use the pencil to mark the location.
Move the stud finder vertically along the wall from the pencil mark. Watch the finder and mark any points where the needle stands straight. Continue until you have made three or four marks to verify the location of the stud.