I've just come across about 3 or 4 wall outlets in my parent's home that are
of the style that will only receive a male plug of 2 prongs. What is
involved in replacing the box innards with the receptacle that will take the
male plug of 3 prongs (2 plus the third below and in the middle)? My
recollection from school days is that the major difference is the addition
of a ground wire to a screw in the middle of the receptacle. Or, am I
thinking of something altogether different. The rest of their house has the
3 prong receptacles so this really is a bit of a mystery.

Charlie.