CP-04Check for cables and pipes, and know your isolation pointsRun a detector over both bracket positions, but treat it as a warning, not a guarantee — detectors can miss cables that run deep, sit in metal conduit, or hide behind metal-backed plasterboard, and old lath and plaster walls confuse cheap detectors badly. Before you drill, find your stopcock (usually under the kitchen sink) and check it turns freely, so you can shut off the water fast if you hit a pipe. If you have any doubt at all, isolate the relevant circuit at the consumer unit before drilling, and don't drill directly above sockets or switches where cables commonly run vertically.