The dog has to use a combination of instinct, skill, and perseverance to get the sheep into the holding pen. The handler can issue commands, but can't let go of the rope attached to the pen's gate. After the sheep are penned, they are then re-released, and the dog has to separate one of them from the flock. Each dog starts with something like 110 points, which are taken away by judges for various mistakes. A score of 90 is pretty good.