A dog undercoat rake is used to remove loose hair from a dog's undercoat, which is the layer of hair that grows beneath the topcoat. It typically has a long handle with a row of closely spaced, curved metal teeth. The teeth are designed to reach deep into the dog's undercoat to remove any loose hair or fur that may be trapped there.
Undercoat rakes are particularly useful for breeds that have thick, double coats, such as German Shepherds, Huskies, and Golden Retrievers. These breeds shed heavily, especially during seasonal coat changes, and an undercoat rake can help to remove the loose hair before it has a chance to become tangled or matted. By using an undercoat rake regularly, you can help to keep your dog's coat healthy and free of mats, and reduce the amount of shedding in your home.