Transparent plates containing lines more widely spaced at one end than the other. By selecting the appropriate taper line grating and placing it parallel to a set of threads in a woven fabric, it is possible to ascertain the number of threads per unit length (cm or inch) as a result of a star form created. These gratings can also be used to determine the number of courses per unit length in weft-knitted fabrics, or the number of dents per unit length in a reed.
Textile Resource (http://www.textile.org.uk)
