SK-03Work out what's behind the wall before you drillUse a stud/metal detector along the wall. A line of regular clicks or a magnet catching on screw heads usually means a timber stud wall; a similar line with no timber pilot-hole dust, but fine steel swarf instead, means metal studs. A dull, hollow knock with no stud pattern behind plasterboard usually means dot-and-dab over solid masonry. A solid, dense knock with no hollow sound means solid brick or block. On older houses, thin ridges felt under the plaster at roughly 400mm spacing suggest lath and plaster. Cables and pipes can run almost anywhere, so even after using a detector, assume something could still be there until you prove otherwise — detectors miss cables that are deep, in metal conduit, behind metal-backed plasterboard, or outside the usual safe zones, and a metal stud frame can confuse a cheap detector further. Find your stopcock now (usually under the kitchen sink) and check it turns, so you can shut the water off fast if you hit a pipe. If you're at all unsure, isolate the circuit at the consumer unit before drilling.