1. With pattern and color tone, put the qualified board and the tested board flat on the ground, standing at a distance of 1.5m from the board for visual inspection.
2. Manually gouge the board flat on the ground, and visually inspect it at a distance of 1.5m from the board.
3. The number of color lines The number of color lines.
4. The length, width and height of the defect are measured with a vernier caliper; the number of missing corners is visually measured.
