SS-03Mark the fixing line and check what's behind the wallHold the wall channel or bracket in place and use a spirit level to mark the fixing holes dead vertical and level with the shower tray. Before you drill, run a cable and pipe detector over the marked line — but still treat the wall as if something could be there, since detectors miss cables in metal conduit or run deep behind tiles. 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 about what's behind the marks, isolate the circuit at the consumer unit before drilling.