Ligne
The ligne, 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 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.
Current use
Watchmaking
There are 12 lignes to one French inch. The standardized conversion for a ligne is 2.2558291 mm, and it is abbreviated with the letter L or represented by the triple prime,. One ligne is the equivalent of 0.0888 international inch.This is comparable in size to the British measurement called "line", used prior to 1824.