The Prisoner has a round peg, but is faced with a square hole. Yet as he slowly lowers the peg into the square hole, it suddenly changes to a round hole!
In the episode of A Change of Mind Number Two tells Number Six that to the Village and its committee he is simply citizen Number Six, and if necessary he will be "shaped to fit." Only in the above aptitude test, it is clearly given that it is the square hole that is prepared to be shaped to fit. The square hole being the Village, and the round peg the Prisoner. 'Squaring the cirlce' I believe it is called.
I'll be squaring up and rounding off the rough edges myself any day now!
Be seeing you