Nail / Screw Finder

I saw in a video recently a guy who is looking to find the studs behind the drywall. He used a magnet thing to find screw/nail heads in the drywall. I thought it looked like fun so I designed this one. I glued a square magnet (15x15x7mm) internally which I had from old computer hard drives. I think you could probably find some on Amazon too. I added the ability to hang a string under it with a light weight (like a small washer) so that you now can get a line on where the stud goes.