 Although the vast majority of coats of arms ever used across the whole of Europe follow the rule, a very few coats which contravened the rule were borne in the mediaeval era by certain families or corporate bodies for many centuries without effective censure by the heraldic authorities.The reason for the original contraventions and for the toleration of them is unknown, although in the case of the arms of the Kingdom of Jerusalem clearly extreme high status was involved.The main duty of a heraldic device is to be easily recognisable.