How to use a stud finder - Stanley 77-720 Stud Sensor 200

The stud finder works by picking up density of the product it is pressed and slid on..Turn your stud finder on make sure the ok light is on...then slightly press it against the wall or surface you are working with,,then slowly moved it right or left still against the surface. As the finder starts to detect more density "thickness" it will. Glow or beep depending what type you have..It will get brighter,louder or what ever it signals are while crossing the stud beneath the surface..keep moving until it stops then move back
again until it stops.....mark or note the position where the signal starts then find the middle...2x4's are 1 1/2 inches across...so center should be 3/4 of an inch...good luck..