Goal: How to use an earth magnet to find a stud in the wall.

Which of the following methods is more reasonable for accomplishing this goal?

OPTIONS:
- Slide it over the wall until it sticks. It finds the screws that attach the drywall to the clamps.
- Slide it over the wall until it sticks. It finds the screws that attach the drywall to the studs.
Slide it over the wall until it sticks. It finds the screws that attach the drywall to the studs.