The second main movement is the flexion and extension of the parallel bars arm, which cooperates with the oblique bird to change the shape of the pectoral muscles. Flat bench press can only practice the middle thickness. Just doing bench press will turn the pectoral muscle into two balls, which is extremely difficult to see.
The shape of the third pectoral muscle is related to genes. Some people are born round or triangular, and no matter how they practice, they can't practice the square like armor. There is no way to improve this, we can only rely on the above practice.