Upholstery is the work of providing furniture, especially seats, with padding, springs, webbing, and fabric or leather covers. The word upholstery comes from the Middle English word upholder, which referred to a tradesman who held up his goods. The term is equally applicable to domestic, automobile, airplane and boat furniture, and can be applied to mattresses, particularly the upper layers, though these often differ significantly in design. A person who works with upholstery is called an upholsterer; an apprentice upholsterer is sometimes called an outsider or trimmer. Traditional upholstery uses materials like coil springs (post-1850), animal hair (horse, hog and cow), coir, straw and hay, hessians, linen scrims, wadding, etc., and is done by hand, building each layer up. In contrast, modern upholsterers employ synthetic materials like dacron and vinyl, serpentine springs, and so on.