Coarse-thread drywall screws have a deep, widely-spaced thread that grips wood fibres aggressively, drives fast, and resists pull-out. This is the correct choice whenever you are fixing plasterboard to timber studs, ceiling joists, or a battened-out wall. The black phosphate finish you usually see is fine for normal interior use — it is a low-friction coating that helps the screw drive, not a corrosion guarantee.

The bugle (trumpet-shaped) head is doing real work here. As the screw seats, the curved underside compresses the paper face gently and dimples it just below the surface, ready for jointing compound. The aim is to set the head a fraction below flush without breaking through the paper, because once the paper is torn the screw loses most of its holding power in the board.

Metal-stud partition systems are increasingly common in UK new-build and commercial fit-out. A coarse wood thread does not grip thin steel well — it tends to spin and strip. Fine-thread drywall screws have a shallow, closely-spaced thread and often a self-drilling or needle point that cuts cleanly into light-gauge steel C-studs and track. The result is a positive bite into the metal without a separate pilot hole on standard 0.5–0.7mm gauge framing.

For thicker or heavier-gauge steel, a true self-drilling (Tek-style) point is needed to penetrate without wandering. Match the screw to the steel gauge stated by your partition system supplier — fine-thread for standard light-gauge sections, self-drilling for anything heavier.

The black phosphate finish on a standard drywall screw offers little corrosion protection. In a heated, dry interior this rarely matters. But behind a moisture-resistant board in a bathroom, in a kitchen, in a utility room, or in any unheated or potentially damp space, an untreated screw can rust — and the rust can eventually bleed through the skim or wallpaper as a brown spot.

For those locations, choose a zinc-plated or galvanised drywall screw, or pair moisture-resistant (green) plasterboard with a corrosion-protected fixing. The extra cost is small and avoids staining that is impossible to clean off without redecorating.

For walls, screws are typically set at around 300mm centres along each stud; ceilings are usually fixed more densely, often around 230mm, because the board is fighting gravity continuously. Keep fixings back roughly 10–15mm from cut board edges so the screw doesn't crumble the edge, and stagger the joints between adjacent boards rather than lining them all up.

Use a drywall screwdriver with a depth-setting nose cone (a "dimpler") or a clutch set so every screw stops at the same depth — just dimpling the paper, never breaking it. A screw driven too deep tears the paper and loses its grip; one left proud stops the next coat sitting flat. Consistency is what makes a board ready to skim.

Expansion plasterboard plugs and self-drive (screw-in) fixings are the workhorses for light jobs. A self-drive fixing has an aggressive external thread you simply wind into the board with a screwdriver — no pre-drilling — then you drive a screw into its centre, which expands or locks it behind the board. Nylon and zinc versions are both common. They suit small mirrors, lightweight frames, curtain pole brackets (shared across several fixings) and trailing-cable clips.

As a rough guide, treat these as good for a few kilograms per fixing in 12.5mm board. They're convenient and tidy, but they're not the answer for anything heavy — don't ask a single light plug to hold a loaded shelf.

A hollow-wall anchor — often called a Molly bolt — is a metal sleeve that you drill in, then tighten so the sleeve crumples and forms legs that clamp the back of the board. Once set, you can remove and refit the bolt repeatedly, which makes them ideal for items that get taken on and off, like a wall-mounted bracket or a removable fixture. A setting tool gives the cleanest result, though some can be set by hand-tightening the bolt.

They spread load better than a simple plug and handle medium weights comfortably in 12.5mm board. Match the anchor's grip range to your board thickness — each size is rated for a band of material thicknesses, and one set for thicker board won't clamp thin board properly.

Toggle fixings reach through a drilled hole and open out behind the board to spread the load across a much wider area than any plug. A spring toggle has two sprung wings that snap open inside the cavity; a gravity toggle drops a bar that sits across the back. Because the load is carried over a broad footprint of board, toggles handle noticeably heavier items than plugs or anchors — they're a sensible choice for shelving and wall cabinets where there's no stud.

The trade-off is that the toggle is usually lost in the cavity if you remove the bolt, so they're less convenient for items you'll take down again. Drill the hole the toggle needs (it's larger, to let the folded wings pass through), and remember the bolt length must allow the wings to clear the back of the board before they spring open.

For the heaviest plasterboard fixings — large TVs on articulated arms, kitchen wall units, heavy radiators where you genuinely cannot reach a stud — purpose-engineered winged cavity anchors carry the highest published ratings. These slot through a neat hole, fold open behind the board, and present a captive thread you bolt into; the better systems quote substantial load figures and let you remove and refit the bolt. Always read the manufacturer's stated rating for your specific board thickness, because the same fixing in thinner board holds far less.

Even so, treat very heavy items with caution. For the truly heavy — large flat-screens, boilers, full kitchen runs — the safest answer is not a cavity fixing at all, but fixing into the studs, or fitting a timber pattress (a board spanning two or more studs) behind or in front of the plasterboard to give a solid, load-spreading base. Cavity anchors are excellent within their limits; they are not a substitute for hitting structure when the load is large.

A screw that turns endlessly without tightening has chewed out the soft gypsum and has nothing to grip. The fix is to step back to the right product: a cavity fixing sized for the load, or relocating the fixing to land on a stud. Trying to "fill and re-screw" the same crumbled hole rarely works — the gypsum around it is already crushed.

If a fixing has already failed and left an enlarged hole, move along to fresh, undamaged board, or use a larger toggle whose wings bear on sound material well away from the damaged spot.

When fixing boards, driving the screw too deep punches through the paper face. The screw then grips only the gypsum core and loses much of its holding power, and the torn recess is harder to fill cleanly. The cause is almost always a driver run at full depth with no stop.

Fit a depth-setting nose cone or set the drill's clutch so every screw stops at the same dimple depth — paper just compressed, not broken. If a screw is already overdriven, back it out and place a fresh one a short distance away rather than driving the same one deeper still.

The dramatic failure — a TV or cabinet tearing free — comes from asking a cavity fixing to do a stud's job, ignoring the leverage of an item that projects from the wall, or hanging everything from too few points. Plasterboard simply cannot carry large, leveraged loads on a couple of small anchors.

For anything heavy, fix into studs, fit a pattress board across the studs to spread the load, and use multiple correctly-rated fixings with a safety margin. If you're unsure whether a wall can take the weight, treat that uncertainty as a "no" and add structure behind the board before you hang the item.

Brown spots appearing through skim or paint in a bathroom or kitchen are usually corroding board screws behind the plaster. A standard black phosphate screw has little corrosion protection, and moisture eventually rusts it through to the surface. The only real cure once it's happened is to dig out, treat or replace the screw, and make good.

Prevent it by specifying zinc-plated or galvanised screws in any damp, wet or unheated location from the start, paired with moisture-resistant board where appropriate. It costs very little at the fixing stage and saves redecorating later.