Let there be no mistake, I do understand the concept of Pivot Center.
The reason of my thread is that there has to be a reason why it is put in the 7th edition, and I have talked to other AI´s about the subject, and I have received different interpretations on this sentence.
You can read it as the hinge pin should be vertical during the hole swing or that the pin can tilt to one side or the other as long as the end in the ground do not move from it´s position, which is precisely between the feet. The mental picture I have in front of me is like a metronome.