The normal value of the lower lung border mobility is between 6-8 cm, usually by doing a physical examination, and the lower lung border is usually located on the left and right sides, symmetrically on the mid-clavicular line, mid-axillary line and scapular line. Let the patient breathe calmly, and then start the percussion from the clear sound of the lung lobes. Normally, the lower lung borders are located in the 6th, 8th, and 10th intercostal spaces of these 3 areas, respectively. If there is a decrease in the mobility of the lower lung borders, pathological causes such as emphysema, atelectasis, pulmonary fibrosis, pleural effusion, and pneumothorax should be considered clinically.