These devices help in training pointing dogs to remain steady and retrievers to sit on flush. They hold a live bird, which you release with a pullcord or remote transmitter. The most basic model is simply a wire basked that you tip up with your foot to release the bird. Then there are mechanical versions with spring arms, a trigger mechanism and a soft mesh basket. Once triggered, the launcher tosses the bird into the air, allowing it to take flight. In the field, you work your dog downwind of the planted bird.