An attachment to a fence, such as a chain link fence, used to confine a dog, prevents the dog from climbing the fence or using the top of the fence to assist himself in escaping over the fence. The attachment creates a region of instability, superjacent the top of the fence, which will not support the dog's weight and thus does not allow the dog to cling to or push off of the top rail of the fence. The region of instability is created by a freely rotatable roller attachment or a flexible panel attachment, both of which yield under the weight of the canine.