Upholstery coil springs are an important part of most modern upholstery. The consumer usually never sees the construction features of an upholstered piece. The overall quality of the materials and construction dictate the comfort level of an upholstered piece and its ability to satisfy the consumer over the long term. A basic upholstered piece may be composed of a frame, springs, foam, cushioning, padding, and textiles. Coil springs are individual coils, open at both ends. They may be knotted at one end. When attached to webbing and twine-tied at the top, they form the platform on which the loose cushion rests. History Ancient coiled helical or spiral shaped wire objects resembling springs have been discovered in the Balkans and across Europe by archaeological teams. Such objects dating from as far back as 4000 BC, the beginning of the first Bronze Age, abound in museums and collections. Wire coiled objects, possibly designed as rings or jewelry, nevertheless exhibit the properties of extension or compression springs. Three technologies drove the development of coiled springs in the mid-1500s, enabled by advances in the quality of steel; these were time-pieces (e.g., clocks and portable watches), firearms (e.g., cannons and pistols), and vehicles (e.g., coaches and carriages). The latter emerged in 16th-century Hungary. Sir William Felton's Treatise on Carriages of 1793 and George Thrupp's History of Coaches of 1877 give examples of evolving applications of springs in transportation that directly transferred to furniture. Germany and Sweden were known even in fifteenth-century Europe as having the best steel because indigenous iron had .05-.07% carbon, which is excellent spring grade iron for steel. In 1690, Sir Ambrose Crowley used German Syrian steel for quality watch springs. Sir Robert Hooke wrote his Lecture on Springs in 1678. In it he explains how anyone can take well formed wire of various compositions and wind it around a form to create a spring. His work demonstrated the phenomenon known today as Hooke's Law, which characterizes springs as providing a restoring force proportional to the extent of their deformation. Clive Edwards, furniture historian, wrote, "One of the most tantalizing questions in eighteenth century furniture is that of springing. Commonly thought to have been a nineteenth century innovation, there is evidence of earlier use. The initial demands for springs appear to have come from the coach builders and the second came from furniture-makers. Coach builders were seeking to improve the ride of