The ligne (pronounced [liɲ] ), or line or Paris line, is a historic unit of length used in France and elsewhere prior to the adoption of the metric system in the late 18th century, and used in various sciences after that time. The loi du 19 frimaire an VIII (Law of 10 December 1799) states that one metre is equal to exactly 443.296 French lines. It is vestigially retained today by French and Swiss watchmakers to measure the size of watch casings, in button making and in ribbon manufacture.