 At the time, at race meets, a large board would display the odds of horses. And the odds were listed for a horse to win, place or show, which was to make third. And if a punter placed a bet across the board, he put an equal amount of money on a horse to finish first, second or third. So it was an across-the-board bet that applied to everything, every option. To add another string to your bow is another sporting expression, which comes from the sport of archery.