Larger knots form when a part of the dog's coat has been neglected for some time. (miracleshihtzu.com)
Large knots in wood should always be sealed with proper wood sealer before being primed with an acrylic product. (abstractartlesson.com)
Dr. Craig says large knotted rope chews are helpful as well, but very hard things like nylabones, cow hooves and butcher bones can be dangerous and harmful to teeth. (everydayhealth.com)