Yes use a straight edge to find buried boxes behind sheet rock. What is a PITA is W/P receptacles, exterior fixtures behind stucco. It is all a reflection on the quality of help that sheet rockers & stucco firms employ.
it's a story i've told here before, but one of my first journeymen, faced with the
stucco crew filling boxed completely, started locating the box head high,
breaking out both sides of each stud, starting at the corner, till he found the wire,
then following it down to the box. he did three houses in a row that way.....
the fourth house had no box, as the rough crew missed it. he put a box in the last hole
with a tail sticking up the wall....... :ashamed1: