On Fri, 5 Aug 2011 16:06:10 +0100, "N_Cook" wrote:

While at it, are the holes in each flat pin , for anti-tugging latch pins ?
Close - spring loaded pins with a ball-shaped end, designed to hold
the blade in the outlet. As better alloys were developed the
construction became much simpler, but the detents remained.

PlainBill