We’ve backed a horse with £25 at 3.5 at Bet Victor, and layed it with £25 at 3.5 on Betdaq earlier in the day.
Now just before the race, Bet Victor’s odds have drifted on the same horse to 5.
So we find a calculator, enter the stake of £25, the new back odds of 5, and the same lay odds of 3.5.
The calculator will show you could lay £35.71 at odds of 3.5 to guarantee a profit of £10.71.
However we have only layed it earlier with £25, so we need to put in a new lay bet of £10.71 at 3.5 to make up the difference, and allow it to go in play to be matched during the race.

If that extra lay isn’t taken, we haven’t lost anything, but if it is then we’ve made a free £10.71. If you can make that every day you’ll be sitting on £300 a month.