A stop prevents the shutter dog from over rotating and a strong rare-earth magnet holds the dog against the shutter to greatly reduce rattling in the wind. Compact design is virtually invisible to preserve the classic look of shutter dogs. Can be surface or flush mounted. Far superior to the "hook" design used by competitors. Stainless steel with nickel-plated magnet for long life. WeatherWright™ certified. Sold as a pair to handle two shutter dogs.