It's 9pm on a Sunday evening and you have a single fixed-odds bet running on Fred Funk in the latest PGA Tour event. The 49-year-old American currently sits in 50th place, 12 shots behind the leader with four holes to play.

Your bet is effectively dead. Imagine, though, if you'd had a spread bet on his finishing position. In that case your bet would be well and truly alive. Picture the scenario - before the event, you sold Fred Funk at 38. If he finishes 50th you end up a loser. But if he shoots a couple of birdies over the final four holes, your bet may turn into a winner.