Configurations
In order to accommodate the dimensions of both football and baseball fields, the stadium was constructed with half of the lower (Field Level) level seating built of permanent concrete (in the southern quadrant of the stadium), and the other half of portable modular construction using aluminum or steel framing.
When the stadium was configured for baseball, the portable sections would be placed in the western quadrant of the stadium along the third base-left field side. Open bullpens were located along both foul lines just beyond the ends of the Field-level seats.
In the football configuration, the portable seating sections are placed in the northern quadrant of the stadium (covering what is used as left field in the baseball configuration) to allow for the football field to be laid out east-west (along the first base/right field foul line, with the western end zone placed in the area occupied by the portable seating sections in the baseball configuration, and the eastern end zone along the right-center field wall).
Doorways are cut in the walls of the stadium in order to allow access to these seats from the tunnel below the Plaza level in both configurations (in baseball configuration, the football doors could be seen above the left field inner wall; in football configuration, the baseball doors are visible above the west end zone, opposite the scoreboard). These doors are rolling metal overhead doors, with the field side painted to match the surrounding walls facing the field.
Read more about this topic: Qualcomm Stadium