DF-03Work out what's behind the frame and pick the right fixingRun a magnet or stud detector along the wall near the frame - a steady line of screw heads under plasterboard means a timber stud, a magnet that clicks onto flat steel means a metal stud. Tap the wall: a dull thud means stud or masonry, a hollow sound means the gap between studs. Drill a small 2mm test hole in an unseen spot - pale dust means timber, fine grey swarf means metal, and brick or block dust means solid masonry. Use a wood screw into the centre of a timber stud, a self-drilling metal-stud fixing or hollow-wall toggle for a metal stud (never a plain plug or wood screw, which strips straight through 0.5mm steel), a wall plug sized to your screw in solid brick or block, and a longer fixing (usually 60-75mm) through dot-and-dab board into the masonry behind.