Excerpt - page 27: "... simpler and less messy approach is to use an electronic studfinder. Early models of studfinders used magnets to lo- cate the nails or screws driven into the ..."
Excerpt - page 167: "... One approach is to buy a "studfinder" (which is not what you naughty ladies may think it is) and sweep across the wall until the magnet in the studfinder registers it has found something metallic ..."