Looking at previous pictures I realized that I hadn't taken a picture of the jig that was used to mark the lines to go from 4 sides to 8 sides.  The points of the two gray nails extends through the wood block and are held against the two sides of the square, tapered fore top mast.  The two pencils also extend through the wood block and mark the two lines.  All four sides are marked in this way and then the corners are planed off down to the lines.