In doubled up comps, you don't normally slip your own dog, a slipper slips both at the same time, giving the hare a start. The dogs are judged against each other on a point system. In the singles it's best of 3 or 5, and then until one misses. If you've got money on a match, which can be thousands, your not gonna stand there watching a hare get to the other end of your field before you slip.