I have some hanging wall cabinets that have a 3/4" particle board back. I believe they are screwed onto the wall but the screws have been covered and then the cabinet back was painted. The wall behind the cabinets is wallboard over 2x4s. Other than completely tear up the wall, I can't figure out how to get them off. Anyone have a trick for finding screws that have been covered with spackle or joint compound and then painted over?