LP-03Work out what's behind the lath and plasterLath and plaster is thin timber strips nailed to studs or battens, covered in a lime plaster skim - the plaster alone won't hold a fixing, so you need to find solid backing. Run a stud detector or magnet over each marked point: a line of nail heads shows where a lath crosses a stud, a dull solid knock usually means masonry behind the laths, and a hollow springy knock means you're between studs. Old houses are often patched with plasterboard after rewiring or damp repairs, so if a patch feels flatter and taps differently, treat it separately and check it against the timber-versus-metal-stud test in the next step. Before you drill anything, find your stopcock (usually under the kitchen sink) and check it turns, and if there's any real doubt about what's behind the wall, isolate the circuit at the consumer unit first - a detector can miss cables that are deep, in conduit, or outside the usual zones, especially in an old wall.