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Lockable socket cover: which kind, then how deep

Updated: 23 October 2026

You are choosing a lockable socket cover because a plug keeps being pulled, or because a shared socket should not be free to switch. The wrong one leaves a fridge live when you wanted it locked off, or locks the point off when a telecare charger had to stay on. This page is the job, then the measurement from the wall to the plug. Prices stay on the [socket lock comparison](/hub/sockets-and-extension-leads/socket-lock). We used those amazon.co.uk listings, PlugMinder's depth pages, and the Knightsbridge CU9LOCKN maker sheet, on 21 October 2026. We did not lab-test the covers. A qualifying purchase can earn a commission at no extra cost to you.

You are choosing a lockable socket cover because a plug keeps being pulled, or because a shared socket should not be free to switch.

Our top picks

Knightsbridge Knightsbridge CU9LOCKN

Best overall

Knightsbridge Knightsbridge CU9LOCKN
6.7/10about £13.88
View offer
PlugMinder PlugMinder 80 mm cover

Rank 2

PlugMinder PlugMinder 80 mm cover
8.6/10about £21.99
View offer
PlugMinder PlugMinder 38 mm cover

Best value

PlugMinder PlugMinder 38 mm cover
8.2/10about £18.99
View offer
On this page
  1. 1.Three jobs, three products
  2. 2.Measure depth before you trust 38 mm
  3. 3.Gang, pattern, and the back box
  4. 4.What stays on the comparison

Three jobs, three products

A household lockable socket cover closes over a plug that stays in. In this set that is the PlugMinder double: B0DJBKJMJ8 at £21.99 for 80 mm, and B0DJBMH2NK at £18.99 for 38 mm. Both files show 4.6 from 43, and the review text is the same block, so use 43 once. The bullets include two tools and a window that is green when unlocked and red when locked. The maker's pages say keys. Use the Amazon bullets for what the listing puts in the box. Knightsbridge CU9LOCKN, B0DKPFKTCS, is £13.88. It locks one Type G outlet on or off. It does not hold a fridge plug that must stay in. Marhynchus, B0DJWDZR87, is £12.88, an industrial kit with a 40 mm inside diameter. Type G is not in that file. Do not buy it as a British 13 A cover.

Measure depth before you trust 38 mm

PlugMinder's range page says you measure from the wall surface, not from the face of the plate, to the furthest point of the plug or the cable bend. The maker uses 28 mm, 38 mm, 58 mm and 80 mm. This comparison only holds the 38 mm and 80 mm doubles. Many standard plugs sit inside 38 mm on that rule of thumb. A transformer-style plug is why 80 mm exists. That is the maker's guidance, not a measurement of the lead in your hand. Shared reviews show moulded plugs that needed the bottom cut so the cable could leave. One review is a 58 mm order, not a depth in this table. If the tape is under 38 mm on an ordinary 13 A plug, compare the 38 mm listing. A plug-top brick is the 80 mm title.
Knightsbridge Knightsbridge CU9LOCKN

Testsieger

Knightsbridge Knightsbridge CU9LOCKN
6.7/10about £13.88
View offer

Gang, pattern, and the back box

Say Type G only when the listing says it. The 80 mm PlugMinder file prints Type G. The 38 mm file does not. The maker's FAQ aims double plates at about 152 mm by 90 mm. Use that as a maker note, not as a line on the 38 mm Amazon file. Warmhm, B0FP1LDPMD, is £10.49. The title says UK and US, with a footprint of 5.89 by 4.32 inches, no Type G line and no gang. The listing says Screw-In, and one UK review describes a self-adhesive pad. Sewroro, B0HD78MSBM, is £9.89, with keys in the title, no rating, and no Type G line. CU9LOCKN is one outlet. One UK review requires a 35 mm back box, and the ML datasheet agrees: 35 mm, BS 1363-2, 230 V, IP20. Amazon says Metal. Screwfix lists £16.69 including VAT and a plastic finish. Do not copy 35 mm onto a different Knightsbridge model.

What stays on the comparison

Amazon prices in this set run from £9.89 to £21.99. Count the shared PlugMinder block once: 4.6 from 43. Knightsbridge is 5.0 from 3, Warmhm is 4.8 from 7, Sewroro has no rating, and Marhynchus is 1.9 from 2. If the plate will not ease forward, or the job is a new socket, that belongs on how to fit a lockable socket cover.

Common questions

Do I need a cover, a key-lock socket, or a lockout?
You need a cover when the plug must stay in and stay powered, such as a fridge, a router, or a telecare charger. You need a key-lock socket when the outlet itself must be locked on or off. That is a replacement plate with a key, not a box over the plug. You need a lockout when a plug has been withdrawn for maintenance and must not be put back. The Marhynchus file is that shape here, and it does not state Type G.
How do I measure plug depth for a UK socket cover?
Measure from the wall surface, not from the front of the faceplate, to the furthest point of the plug or the cable bend, with the lead in the direction it will leave. PlugMinder's classes are 28 mm, 38 mm, 58 mm and 80 mm. Only 38 mm and 80 mm are rows in this set. If you are close to the limit, take the deeper class rather than hoping the cable will squash flat.
Is 38 mm enough for a moulded plug?
Often it is not, even when the projection looks modest. In the shared PlugMinder reviews, moulded plugs needed the bottom of the cover cut so the cable could exit. A bulky body can foul that exit before it runs out of depth. If the plug is a simple 13 A shape and the tape says under 38 mm, the 38 mm listing is the one to compare.
Does 'fits UK and US' mean a British double plate?
No. The Warmhm title says UK and US and prints a footprint in inches. The attributes do not say Type G and do not say how many gangs. PlugMinder's own FAQ puts a British double at about 152 mm by 90 mm, which is a different check. Sewroro does not state the pattern at all.
Is a 40 mm industrial lock the same product as a 13 A cover?
No. Forty millimetres on the Marhynchus title is an inside diameter for an industrial connector, not a plug depth in front of a UK wall socket. The rank line is lockout and tagout devices. The file does not call it Type G, and it does not show a padlock in the box. A household cover that keeps power on is a different tool.

Related pages

Socket lock vs plug-in covers

Socket lock

Best socket lock UK: one cover, one key-lock socket

Socket lock dementia: keeping the essential plug in

How to fit a lockable socket cover, then when to stop

Sources

Sources taken from the research digest. Listings were scored on 21 October 2026. This page did not run a lab test.

  1. Plugs and Sockets etc. (Safety) Regulations 1994 (retrieved 21.10.2026)
  2. IET Wiring Matters, socket-outlet protectors (February 2020) (retrieved 21.10.2026)
  3. BEAMA position paper on socket outlet covers (5 June 2017) (retrieved 21.10.2026)
  4. Electrical Safety First — socket covers (retrieved 21.10.2026)
  5. Electricity at Work Regulations 1989, regulation 12 (retrieved 21.10.2026)
  6. HSE HSG85 (retrieved 21.10.2026)
  7. Approved Document P (England, 2013) (retrieved 21.10.2026)
  8. CU9LOCKN datasheet — ML Accessories (retrieved 21.10.2026)