TR-02Check for pipes and cables, and know your stopcockRun a cable and pipe detector over the wall before you mark anything, but don't trust it completely — detectors miss cables that are deep, in metal conduit, or behind metal-backed plasterboard, and bathrooms often have hidden pipework for a shower or basin. 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 about what's behind the wall, isolate the electrics at the consumer unit before drilling.