Independent comparisons. We may earn from shop links. More info

Plasterboard cavity fixing gun for a stud-wall bay

Updated: 22 October 2026

You have 12.5 mm plasterboard on a timber stud wall, and you want a rail, a mirror or a light shelf. A plasterboard cavity fixing gun only helps once you have decided the screw belongs in the empty bay. Use the timber for a shelf if you can find it. Use the gun and a metal sleeve only for a light fix in the void, inside the board maker's example, not as a substitute for a stud you can reach. The tool cards are on the [hollow wall anchor setting tool comparison](/hub/screws-and-accessories/hollow-wall-anchor-setting-tool). Peter F. used British Gypsum's published example, not a test of these amazon.co.uk kits.

You have 12.5 mm plasterboard on a timber stud wall, and you want a rail, a mirror or a light shelf. A plasterboard cavity fixing gun only helps once you have decided the screw belongs in the empty bay.

Our top picks

TOPWAY TOPWAY molly gun

Best overall

TOPWAY TOPWAY molly gun
9.2/10about £9.79
View offer
Brackit Brackit 88-piece kit

Rank 2

Brackit Brackit 88-piece kit
8.8/10about £18.99
View offer
Becho Becho gun and plugs

Alternative

Becho Becho gun and plugs
8.6/10about £17.88
View offer
On this page
  1. 1.What kind of plasterboard you have
  2. 2.Stud first, sleeve second
  3. 3.The 12 kg example
  4. 4.When not to use the gun

What kind of plasterboard you have

The usual single layer on a UK stud wall is Gyproc WallBoard at 12.5 mm. The bay is empty, and a plastic plug has nothing to expand against once it passes the paper. A metal hollow-wall anchor opens in that void, with the flange on the room side. A stud finder, or a pilot that meets timber, means the screw can go into the frame instead. Dot and dab is not a free cavity. The path that holds is back to the masonry. If the wall sounds solid, stop. Fischer's HM 5 x 37 is listed for board about 6-15 mm, which covers bare 12.5 mm and does not cover tile and adhesive unless that packet says so.

Stud first, sleeve second

Practical DIY's advice on shelves is to drive the brackets into the vertical timbers. On modern stud walls that guide gives the centres as about 600 mm, which is not a rule for every house. A shelf bracket that can hit a stud should hit the stud. The gun is for the bay you cannot avoid. A rail or a mirror plate is the more ordinary sleeve job, because it hangs close to the wall. A bracket that sticks out turns the sleeve into a lever. Two sleeves in the bay do not become a stud. If the bit hits timber, stop setting a molly and use a wood screw. The squeeze order, once the bay is real, is in how to use a hollow wall anchor setting tool.
TOPWAY TOPWAY molly gun

Testsieger

TOPWAY TOPWAY molly gun
9.2/10about £9.79
View offer

The 12 kg example

British Gypsum's Site Book gives an M5 x 40 expanding cavity fixing, reference D, a 12 kg safe working load in board up to 12.5 mm, with a factor of four. The failure figure beside it is 48 kg. That 12 kg is for the case the book describes. It is not a rating of these amazon.co.uk kits, and four sleeves do not multiply it into a cupboard load. Heavier bands in the same book move to a stud or a channel. You cannot borrow Fischer DuoHM's 20 kg figure, because that plug does not use this gun. A 65 lb line, about 29 kg, sits above the 12 kg example and is still not a safe working load.

When not to use the gun

Do not use the gun on dot and dab as if the dabs were a cavity. The sleeve can open in a shallow void and still miss the masonry. If you are unsure of the construction, look at an offcut by a socket. Do not hang a television bracket, a basin or a wall cupboard on these sleeves because a listing says brackets. One review describes a television that stayed up. That is one report, and the card prints no kilogram. Which listing to open for a light bay fix is on best plasterboard fixing gun. A qualifying amazon.co.uk purchase can earn a commission at no extra cost to you.

Common questions

Is 12.5 mm board thick enough for a molly?
It is the thickness in the Site Book's cavity-fixing example, for board up to 12.5 mm, and it is the common Gyproc WallBoard layer. Thick enough means the sleeve's own range includes 12.5 mm and the load stays in that published illustration. It does not mean any metal anchor will do. A sleeve listed for a much thinner panel can fail to open properly, and a long sleeve can fold too early. Read the packet against the board you measured, including any tile.
What is 12 kg here?
It is the safe working load in British Gypsum's Site Book example for an M5 x 40 expanding cavity fixing in board up to 12.5 mm. The example uses a factor of four, and the failure figure beside it is 48 kg. It is not a test of these amazon.co.uk guns, and it is not a licence to hang 12 kg on every sleeve you own. Heavier rows in that book move to a stud or a channel.
What if the wall is dot and dab?
Treat it as a lined masonry wall, not as a hollow stud bay. The dabs leave an uneven gap, and a sleeve in that gap loads the plasterboard instead of the wall behind. The path that holds is back to the masonry. A plasterboard cavity fixing gun does not bridge that gap. Stop, and do not copy the stud-wall sequence onto dabbed board.
Can I hang a kitchen cupboard on four sleeves?
No. A cupboard is not the Site Book's reference D, and four holes do not turn 12 kg into a cabinet load. Heavier bands in that book go into the stud or a fixing channel. Use the timber frame, or a system the cupboard maker specifies. The same stop applies to a basin. Sleeves in the bay are for light fittings that sit inside the published example.
The listing says it is for TV brackets. May I?
Not on the strength of that sentence. Television brackets are a stop-point on this page. A review that a set stayed on the wall is one person's report, and the listings in this set do not print a tested kilogram you can match to a screen. Fix a bracket to studs or to a rated frame. The gun and a sleeve remain a light bay fixing, not a mount for a television.

Related pages

Hollow wall anchor setting tool buying guide

Molly setting tool vs screwdriver

Hollow wall anchor setting tool

Best plasterboard fixing gun: sleeves or tool only

How to use a hollow wall anchor setting tool safely

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the ten amazon.co.uk listings captured on 19 October 2026. There is no laboratory test. A 65 lb listing line is not a safe working load.

  1. Fischer UK, metal cavity fixing HM (retrieved 19 October 2026)
  2. Fischer UK, cavity fixing DuoHM (retrieved 19 October 2026)
  3. Rawlplug, SM Interset (retrieved 19 October 2026)
  4. Rawlplug, AT-88 setting tool (retrieved 19 October 2026)
  5. British Gypsum Site Book (retrieved 19 October 2026)
  6. Wonkee Donkee, metal anchor expansion tools (retrieved 19 October 2026)
  7. Rapid, how hollow wall anchors work (retrieved 19 October 2026)
  8. Consumer Rights Act 2015, section 9 (retrieved 19 October 2026)