This instrument is to install the drawing paper on the smooth metal ring plate of the cross-scribing instrument, then insert the pencil into the pencil clip and tighten it, adjust the clamping position to keep the mechanical rod balanced, so that the lead can mark the drawing paper to ( Draw lines at a speed of 45-55) mm/s, draw 15 lines at a time, each line length is 60mm, and the spacing is 1.5mm. After drawing 15 lines each time, rotate 45° in sequence and continue to draw lines, a total of four times. . Take a square with a side length of (25±1) mm in the middle of the stitch as the sample paper.