Mk Sockets

[jadyn]

My house is fitted with many MK double wall sockets made of white plastic. The sockets cannot be more than about five years old due to the age of the house. I've noticed that the earth pin holes on the face of the socket are lined on the left and right by what appears to be copper plates.
Does anyone know why the hole is lined in this way? I've not noticed them on other sockets in other peoples' homes or at work and a 13a plug seems just a tiny big more difficult to insert in my home. What are these things called?

Thank you.

[Etch]

The copper bits are the contacts for the plug earth pin. My MK sockets are the same: I imagine that the earth contacts are made like that to ensure the earth pin makes contact with its circuit first, and the appliance is therefore earthed before the live and neutral pins make contact.

[alavahalf]

The earth contact needs to be last one to disengage when a plug is removed from a socket.
A little tip .. wipe a smear of Vaseline on the earth pin on your plug, then remove any excess wiping it clean with your finger.
Try the plug in the socket again and see if there is a difference.

[jadyn]

Thank you both.