TR-03Check for cables and pipes, and know your isolation pointsDetectors miss cables that are deep, in metal conduit, behind metal-backed plasterboard, or run outside the normal safe zones — and a metal stud frame will confuse a cheap detector even more. Treat every hole as if something could be there until you have proved otherwise. Find your stopcock now, 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, isolate the relevant circuit at the consumer unit before drilling near sockets or lights, and turn the water off at the stopcock before cutting into a wall that could carry pipework.