AB-04Fit a deeper box if you need one — the fixing depends on your wallBefore drilling anywhere, sweep the area with a cable and pipe detector, then still treat the wall as live until you've proven otherwise; find your stopcock and check it turns, and keep the circuit isolated at the consumer unit before you cut into anything. In solid brick or block, drill a 6mm hole with a masonry bit and use a wall plug for the box's fixing lugs. In a timber stud — found by tapping for a solid sound, following a line of screw heads, or drilling a small pilot hole that brings out wood dust — screw the box lugs straight into the timber with 32mm wood screws. In a metal stud, spotted by a hollow sound and a pilot hole bringing out fine steel swarf, use self-drilling metal-stud fixings or plasterboard toggles, never plain wall plugs or ordinary wood screws, which strip straight through 0.5mm steel; a USB socket is light enough for these fixings alone. For dot-and-dab or lath and plaster, use a dry-lining ('bendy') box that grips the plasterboard skin with its own wing dowels rather than screwing into the masonry or laths behind.