An Old Trick (for turning squares into octagons)
Anyone who has laid out an octagon on a long square blank using a set of dividers, knows that it would be a lot easier if humans had evolved with three hands. And there are times, as in “posts in place”, shaving fifty leg blanks or an octagonal section placed between two square sections, where laying out on an end is next to impossible. And, then again, you might never have the need for this old carpenters trick. But, here it is, anyway.
On larger square stock, lay a 24″ framing square or rule diagonally from one edge to the other. “Tick” mark at 7″ and 17″. Hand hold a pencil and mark the lines. (Most people are amazed at how accurately a “hand-held” line can be drawn.)
For smaller stock, you can use a 6″ or 12″ scale. Lay the diagonal line from 0″ to 6″. Then “tick” at 1 3/4″ and 4 1/4″. Follow the path above.
You’ll be amazed at the accuracy of this method, not to mention the ease.