It is about the index of weft density of fabric, and it is to check whether it meets the weaving process standard. When the weft is dense, the cloth becomes thick, and the gram weight exceeds the index, the cost will increase. Weft reduction will make the fabric thinner and the grammage is not enough, which does not meet the technological requirements. Fold the three-fold weft dense mirror back into a U-shape, put the round hole surface close to the cloth pattern, and keep your eyes close to the magnifying glass.