This photo shows a Bouvier herding a flock of about 40 sheep down a dirt road in the Mojave Desert of Southern California. There is a bit of snow on the ground. You can see the black dog at the back of the flock : dog and sheep are about the same size. The handler is walking along and relying on the dog to keep the sheep following her. This is the basic "auto-pilot" type of herding work : handler leads and dog makes sheep follow the handler. You can get most practical jobs done in this fashion. Notice that the dog is flanking slightly counter-clockwise in order to tuck back into the flock the sheep that has separated slightly off to the right.