AB-02Work out what's behind the wallRun a cable and pipe detector over the whole marked area, then check for framing: a magnet run down the wall will stick to the screw heads on a metal stud in a neat vertical line, while timber studs give a duller signal and no magnetic pull. Drill a 3mm pilot hole in a spot the rail will cover to confirm — pale wood dust means timber, fine grey swarf means metal, and solid material a few centimetres in with no frame means brick, block, or dot-and-dab. Before you drill, find your stopcock (usually under the kitchen sink) and check it turns, so you can shut off the water fast if you hit a pipe. If you have any doubt about what's hiding in the wall, isolate the circuit at the consumer unit and turn off the water at the stopcock before you go any further.