“I normally refuse to join in campaigns but this seemed so important, and the ‘safety’ covers so absurd and dangerous, that I agreed”
Author, TV presenter & Patron of FatallyFlawed
Dr Adam Hart-Davis



“Sockets in the UK are designed to keep people safe. Our UK design has been better than the majority of other countries, for many years.  Socket covers are an absolute con and totally unnecessary.” 
Engineering, Maths and Science presenter on TV
FatallyFlawed Supporter

Johnny Ball

Socket Damage

IMPORTANT: This information applies to BS 1363 sockets only   

MK Electric has been making electrical fittings since 1919 and shuttered sockets since 1926. The company has gained a reputation for high quality products and for many years  their version of the 13A socket has incorporated a shutter mechanism that needs all three pins of a plug to be in place to open the shutter. They have done this because, like other quality manufacturers, they want their sockets to be as safe as possible. All good quality electrical fittings are rigorously made to carefully considered standards drawn up by groups of engineers with many years of experience.

The MK socket is designed to suit a standard 13A (BS1363) plug - not the other way round. Other responsible manufacturers design their sockets in exactly the same way. This means that any non-standard device which is pushed into the socket may not fit, and it could quite probably damage the socket permanently and dangerously.

This is not a defect in the socket design - the socket will perform correctly with a standard plug; it is simply not possible for the socket designer to anticipate what some irresponsible manufacture of a non-standard plug-like device might produce.

This is what all the blanking plug manufacturers whose products we have been able to find have done - they have ignored the carefully thought-out standard for plugs which has served well since 1947 and produced an article with the wrong size or shape of pins, (apparently, being wrong is good enough for them), in a material which is unspecified and untested. This shows either they simply don't understand the British Standard, or they don't care.

As an example of how even the best of sockets can be compromised by a non-standard  device, look at how the MK shutter mechanism works.  Note, clicking on a picture will open a larger version in a pop-up window.


On the left, a diagram of the MK shutter mechanism and the rear of an actual shutter.  The shutter is latched closed by a pair of sprung claws wrapped around a substantial 'Y' shaped peg.
On the right, a cutaway view of the socket and a diagram of the same.


When a correctly dimensioned earth pin or its plastic equivalent is inserted, the tapered sides of the earth pin open the claws which are then free to move downwards past the Y-peg.
Note that, at this stage, the plug is almost far enough into the socket to leave only the insulated part of the lower pins exposed. The earth pins is also about to make contact with its contacts inside the socket and it will make this contact before the live pins connect. The sloping lower edges of the pins are just coming into contact with the sloping face of the insulating shutter.

Detail_4 _MK

As a standard plug is pushed fully into the socket, the lower pins press against the sloping "wedge-shaped" faces on both sides of the shutter. It is this that causes the shutter to slide downwards against the compression spring, allowing the plug to be pushed right into the socket and so to make electrical contact.


So what happens when a "safety" blanking plug is pushed, even forced, in instead? It's impossible to say, because the blanking plug isn't made to any standard. Its pins may be the wrong shape, the wrong length, too big or too small. They may damage the shutter mechanism or jam it open - and once the blanking plug has been forced in, its pins may be too big for the electrical contacts inside the socket.

These two images show shutters removed from sockets in a rented house where socket covers were in use.  The damage to the shutters (which no longer fully obscure the apertures) suggests that the “earth pin” was too narrow to properly separate the hooks, leaving one side still engaged, excess pressure has then resulted in distortion of the disengaged side, followed by failure of the shutter material.



Some Legrand sockets also use a three pin operated mechanism which depends upon a correctly shaped earth pin being inserted before it is possible for equal pressure on the other pins to open the shutters.  Attempting to insert a socket cover with an incorrectly shaped “earth pin” that does not fully operate the latch may damage the mechanism.


Hager is another quality socket manufacturer with a patented three-pin shutter mechanism.  Pictured right is a Hager socket shown from the rear of the faceplate (the earth contact has been moved so as not to obscure the shutter).  Insertion of an earth pin will partially lift the inverted T member, this allows the main shutter to be operated by the other two pins.


The image above shows the shutter ‘S’ in the closed position.  Latch ‘L’ prevents the shutter moving towards the contact, and projection ‘X’ in the faceplate prevents the shutter from moving aside. 

The three photos below show a cutaway Hager socket allowing a side view of the line contact and the shutter which protects access to it.  The socket has been positioned face up, although it would usually be mounted in the vertical position.
Note, clicking on a picture will open a larger version in a pop-up window.


An earth pin ‘E’ has been inserted (it is in shadow so is hard to see), this moves the latch ‘L’ partially aside, allowing some movement of the shutter ‘S’ towards the contact.

A complete plug has been inserted, simultaneous pressure on the two power pins has allowed the shutter ‘S’ to be pushed aside, displacing the latch ‘L’ further as it does so. 


In the final image an attempt has been made to insert a Clippasafe socket cover.  The two shorter pins are blocked by the shutters, limiting the insertion of the non-conforming “earth pin” which, being angled, is not capable of moving the latch aside, so the shutter remains in place.

If force is used in an attempt to insert the socket cover the mechanism will be damaged, and the shutters will no longer provide protection.

These sockets with three pin operated shutters are examples of high quality products made to conform to BS 1363.  They will provide a high degree of protection to small children and babies.

However, as with any precision product, an adult attempting to insert objects which do NOT conform constitutes foolish abuse of the socket, and may cause permanent damage!

As shown elsewhere on this site, poor contact is a common cause of electrical fires with obvious dangers at any time of day or night.

But that's not the only danger. The third, top, pin is an important safety device. Many electrical appliances need to be earthed through this pin - if they weren't, there would be a danger that a fault might make their casing live and this has been the cause of fatal shocks.

If the earth contact of your socket has been damaged by a non-standard "safety" blanking plug, how long would it take you to find out? Without knowing it, you could be using an appliance which has no earth protection and that could give you, or your child, a fatal shock.

Do you really want to plug a non-standard device into one of your sockets? It may be labelled a "safety" device but who says it's safe?

The only way to keep your family safe is to:

  • Make sure that all your sockets have been made by a reputable manufacturer who keeps to the correct
    British Standards
  • Check that they are in good condition - if you're not sure, have every socket tested
  • Only ever plug in a standard plug or other device which conforms exactly to dimensions specified in BS 1363
  • Remove and destroy any device that is not genuinely made to those dimensions
    - even if it claims to be a "safety" device.

For more on the damage which incorrectly sized socket covers can cause, see the Clippasafe review.

The bottom line is:
Safety is designed into UK sockets - plug in covers reduce safety!

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