Start With the Material, Not the Screw

Most failed DIY fixes have nothing to do with the drill or the driver bit. They come down to grabbing whatever screw was loose in the tin and forcing it into a material it was never designed for. A 4mm wood screw tapped into a brick wall will feel tight for about ten seconds and then spin. A masonry bolt driven into plasterboard will pull a fist-sized crater out of your wall the moment it takes any load. Match the fastener to what's behind the surface and everything else gets easier.

As a rough rule, ask yourself what the screw is gripping. Is it gripping timber fibres, the solid mass of masonry, or just the paper and gypsum skin of a plasterboard sheet? Those three answers lead to three completely different boxes in the hardware shop.

Wood screws: your default for anything timber

Modern wood screws are almost all twin-thread, part-threaded and countersunk, which makes them genuinely good at their job. The coarse thread bites and pulls the two pieces together, while the smooth shank below the head lets the top board clamp down tight without jacking apart. Sizes are sold as gauge by length, so a 4.0 x 40mm is a 4mm diameter screw that's 40mm long.

• Softwood framing and battens: 4.0 x 50mm or 5.0 x 70mm twin-thread screws are ideal for 38mm and 47mm CLS timber.
• Hardwood and dense sheet material: drop to a finer thread and always drill a pilot hole. Hardwood splits easily and a pilot of roughly 80% of the screw's core diameter keeps things intact.
• MDF and chipboard: use screws designed for the job, or pre-drill, and never over-tighten — the core crumbles and the fixing never comes back.
• Outdoors: choose stainless steel or a coated exterior screw. Bare steel will rust and stain your fencing or decking within a season.

Two practical notes. Always drill a clearance hole in the top piece so the screw pulls rather than pushes, and use a Pozi or Torx driver bit that actually fills the head recess — a worn bit rounds off heads faster than anything else.

Coach screws and heavy timber fixings

When you're fixing a gate post to a wall plate, a shed frame to a base, or a heavy timber ledger to a joist, ordinary screws aren't enough. Coach screws, usually 6mm to 10mm in diameter with a hex head, are driven with a socket or spanner and hold serious load. They almost always need a pilot hole and often a washer under the head. For concealed work on timber-to-timber joints, a structural screw with a large washer head does a similar job with a cleaner finish. If there's any doubt whether a fixing is load-bearing, or it's a job that could injure someone if it failed, get it checked rather than guessing.

Masonry fixings: brick, block and concrete

Solid masonry grips by friction against a plug, so the hole diameter matters enormously. Drill the hole the exact size stated for the plug, drill it deeper than the plug by about 10mm so dust has somewhere to go, and blow or brush the dust out before inserting anything. Dust is the single most common reason a wall plug spins uselessly.

Standard nylon wall plugs are colour-coded by diameter, which makes matching them to your drill bit straightforward — a 5mm plug takes a 5mm bit and a screw roughly 4mm to 5mm in diameter, and so on up the sizes. Drill with hammer action and an SDS bit, and stop immediately if you hit a lintel or steel, because masonry bits won't touch it.

For heavier loads — satellite brackets, wall-mounted cabinets, gate hinges — move up to a through-bolt or a frame fixing. Frame fixings are especially useful because you drill once, push the sleeve through the timber into the wall and tighten the screw, all in one operation. Modern concrete screws are another option, cutting their own thread in brick or block with no plug at all, though they need a correctly sized hole and are unforgiving of mistakes.

Plasterboard fixings: hollow walls need hollow-wall anchors

Plasterboard on its own will hold almost nothing. A standard screw will simply tear through the paper. But with the right anchor, a plasterboard wall will happily take a shelf, a mirror or a radiator.

• Self-drill metal anchors: the quickest option for light to medium loads. They cut their own hole, expand behind the board and hold well, provided you don't overtighten and strip the plaster.
• Spring toggles: the strongest common option for medium loads. The toggle flips open behind the board and spreads the load across a wide area. You'll need to make a hole big enough to pass the toggle through, so plan your placement carefully.
• Heavy-duty hollow-wall bolts: a metal sleeve that expands into a wide flange behind the plasterboard. Excellent for heavier items, though the hole is large and unforgiving.

Always check what's behind the board. A stud finder will tell you whether there's a timber stud or a metal frame close by. If a stud is within reach, screw straight into it and forget the anchors entirely — it's stronger, simpler and cheaper.

A quick way to choose

Timber into timber: twin-thread wood screw, pilot hole if it's hardwood or close to an edge. Timber into masonry: frame fixing or coach screw into a plug. Something onto masonry: wall plug matched to the drill bit, bigger plug for bigger load. Something onto plasterboard: a hollow-wall anchor, or a stud if there's one nearby. Keep those four habits, buy your fixings by size rather than by guesswork, and you'll spend far less time repairing holes and far more time finishing the job.