SSH-02Confirm you actually have timber studsRun a stud detector or a magnet along the marked line, tracking screw heads to find the studs, which are normally 400mm or 600mm apart centre to centre. Tap along the wall — a stud sounds solid, the gap between studs sounds hollow. Drill a small 3mm pilot hole at the suspected centre: timber dust confirms a timber stud, fine grey metal swarf means it's a metal stud instead. If you find metal studs, don't use a wood screw or a plain plastic wall plug — they strip straight through 0.5mm steel. Fit a self-drilling metal-stud fixing, or a hollow-wall toggle rated for the shelf's load, and check every bracket point the same way.