Calculated Industries 8105 Blind Mark Drywall Electrical Box Locator Tool Perfect drywall cutouts in half the time with NO measuring using powerful rare-earth magnets Twice as easy and only half the lifting of other marking methods Get professional results you can be proud of your first and every time with foolproof patented technology Pays for itself by avoiding costly and embarrassing measuring errors. Handy rugged case stores, organizes and protects all parts between projects 3 included Targets fit standard single or multi-gang plastic boxes for any NEW construction installation; For receptacles in place, see Plug Mark