AB-04Work out what's behind the wallRun a stud detector or magnet along the wall at your marked height. A line of screw heads roughly every 400-600mm, or a hollow sound when you knock between them, means plasterboard on studs. Tap the wall — solid brick or block sounds dull and dense with no hollow spots. Drill a small pilot hole at one mark: timber dust means timber studs, fine grey swarf means metal studs, and a dull grinding with brick dust means solid masonry. Old horizontal ridges under a soft, uneven plaster surface usually mean lath and plaster. Detectors miss cables that are deep, in metal conduit, behind metal-backed plasterboard, or simply outside the usual safe zones — and a metal stud frame can confuse a cheap detector further. Always expect a cable or pipe could be there and drill carefully, stopping the moment you feel resistance or see anything other than dust. If you're in any doubt, isolate the circuit at the consumer unit before drilling, and know your stopcock is ready in case you hit water.