PB-02Work out exactly what wall you haveDon't assume — check, because the fixing is different for every wall type. Knock across the marked area: a hollow, slightly springy sound with a bit of give means dot-and-dab or a stud wall, and a dead, solid knock everywhere means solid brick or block. Drill a small 2-3mm pilot hole in an inconspicuous spot and look at the dust: fine white powder is plasterboard or old plaster, gritty red or grey dust is brick or block, pale shavings are timber, and shiny metal swarf means a metal stud. On stud walls, run a magnet or detector along the surface — regular clicks every 400-600mm mark stud centres, and a magnet sticking well away from any joint line means metal studs.