How to easily remove the screw cover that is found on the socket on the wall?

Update: Thanks for the replies but what i was actually asking for the removal of screw cover, which is like a small button that is placed to hide the screw. It is usally found at the side of socket.
Update 2: Thanks for the replies but what i was actually asking for is the removal of screw cover, which is like a small button that is placed to hide the screw. It is usally found at the side of socket. It look likes the cap found on the this webpage http://www.ark-plas.com/products/product.asp?classID=10
Update 3: I mean covers and this is the type of socket i was referring to http://www.comp.hkbu.edu.hk/~eee05/venue/HK-Socket.JPG
4 answers 4