SC-03Check what's behind the wall before you drillRun a detector over each mark, but treat it as a warning, not a guarantee - detectors miss cables that are deep, boxed in metal conduit, behind metal-backed plasterboard, or outside the normal safe zones, and a metal stud frame can confuse a cheap detector further. Before you drill, find your stopcock (usually under the kitchen sink) and check it turns freely, so you can shut the water off fast if you hit a pipe. If you have any doubt at all, isolate the circuit at the consumer unit first, and if you're cutting into anything that could carry water, turn it off at the stopcock before you start.