Furs are considered amphibious, and neither metal nor colour; but in practice ermine and erminois are usually treated as metals, while ermines and pean are treated as colours. This rule is strictly adhered to in British armory, with only rare exceptions; although generally observed in continental heraldry, it is not adhered to quite as strictly. Arms which violate this rule are sometimes known as "puzzle arms", of which the most famous example is the arms of the Kingdom of Jerusalem, consisting of gold crosses on a silver field. The field of a shield, or less often a charge or crest, is sometimes made up of a pattern of colours, or "variation". A pattern of horizontal (barwise) stripes, for example, is called "barry", while a pattern of vertical (palewise) stripes is called "paly". A pattern of diagonal stripes may be called "bendy" or "bendy sinister", depending on the direction of the stripes. Other variations include "chevrony", "gyronny" and "chequy". Wave shaped stripes are termed "undy". For further variations, these are sometimes combined to produce patterns of "barry-bendy", "paly-bendy", "lozengy" and "fusilly". Semés, or patterns of repeated charges, are also considered variations of the field. The Rule of tincture applies to all semés and variations of the field. The field of a shield in heraldry can be divided into more than one tincture, as can the various heraldic charges. Many coats of arms consist simply of a division of the field into two contrasting tinctures. These are considered divisions of a shield, so the rule of tincture can be ignored. For example, a shield divided azure and gules would be perfectly acceptable. A line of partition may be straight or it may be varied. The variations of partition lines can be wavy, indented, embattled, engrailed, nebuly, or made into myriad other forms; see Line (heraldry). In the early days of heraldry, very simple bold rectilinear shapes were painted on shields. These could be easily recognized at a long distance and could be easily remembered. They therefore served the main purpose of heraldry: identification. As more complicated shields came into use, these bold shapes were set apart in a separate class as the "honorable ordinaries".