A pair of stacked hard drive magnets. One wasn't quite enough (these newer hard drives not nearly as good) but two would stick to the drywall screw. Find center of magnet, mark the wall, done. As opposed to the hope and poke stud finder that I've had for years (or hoping to find a nail pop someplace).
Finally found a use for those magnets that I've been saving all this time (other than for holding things to the fridge).
Finally found a use for those magnets that I've been saving all this time (other than for holding things to the fridge).