RT-06If it turns out to be a different wall typeSolid brick or block with no air gap: drill a 6mm hole 35-40mm deep and use a standard wall plug and screw. Timber stud: find the stud centre and drive a 4x40mm wood screw straight into the timber, no plug needed. Metal stud: never use a wood screw or plain plastic plug, as it strips straight through 0.5mm steel — use a self-drilling metal-stud fixing or hollow-wall toggle, and if the router will pull on the fixing, fix through to a noggin or the masonry behind instead. Lath and plaster: drill gently to avoid splitting the laths, and use a spring toggle or long screw with a hollow-wall fixing set into the plaster key, not just the lath itself.