arms. Apart from that, flexible metal epaulettes were quite popular among certain armies in the 19th century, but were rarely worn on the field. Referred to as shoulder scales, they were e.g. an accoutrement of the US Cavalry, US Infantry and the US Artillery, from 1854 to 1872. By the early 18th century, epaulettes had become the distinguishing feature of commissioned rank. This led officers of military units still without epaulettes to petition for the right to wear epaulettes to ensure that their status would be recognized. During the Napoleonic Wars and subsequently through the 19th century, grenadiers, light infantry, voltigeurs and other specialist categories of infantry in many European armies wore cloth epaulettes with wool fringes in various colors to distinguish them from ordinary line infantry. Flying artillery wore epaulette-esque shoulder pads. Heavy artillery wore small balls representing ammunition on their shoulders. An intermediate form in some services, such as the Russian Army, is the shoulder board, which neither has a fringe nor extends beyond the shoulder seam. This originated during the 19th century as a simplified version for service wear of the heavy and conspicuous full dress epaulette with bullion fringes. Modern derivations Today, epaulettes have mostly been replaced by a five-sided flap of cloth called a shoulder board, which is sewn into the shoulder seam and the end buttoned like an epaulette. From the shoulder board was developed the shoulder mark, a flat cloth tube that is worn over the shoulder strap and carries embroidered or pinned-on rank insignia. The advantages of this are the ability to easily change the insignia as occasions warrant. Airline pilot uniform shirts generally include cloth flattened tubular epaulettes having cloth or bullion braid stripes, attached by shoulder straps integral to the shirts. The rank of the wearer is designated by the number of stripes: traditionally four for a captain, three for senior first officer or first officer, and two for either a first officer or second officer. However, rank insignia are airline specific. For example, at some airlines, two stripes denote junior first officer and one stripe second officer (cruise or relief pilot). Airline captains' uniform caps usually will have a braid pattern on the bill. These uniform specifications change depending on the company's policy. Belgium In the Belgian army, red epaulettes with white fringes are worn with the ceremonial uniforms of the Royal Escort while fully red ones are worn