I think what I'm confused about are called the aft or mizen brace bitts. On the Discovery1789 the original drawings show bitts at the bottom of the fore and main masts but don't show bitts at the base of the mizen mast. Half of John Mckay's drawings do show them and half don't. Looking around I found that some ships have bitts with belaying pins, and some have ringbolts in the deck and cleats on the mast. Is there a reason for the difference or are they just "different" and its builder's choice?