There are designated standing room only places located between the lower and upper portions of the 300 level sections. These tickets do not have a seat, but instead have a yellow square in which you must stand inside. These squares are located at the back of the walkway which separates the lower rows from the upper rows, so your spot would be just below Row F in Section 307.

Standing Room Only on the 300 Level at CenturyLink Field
Standing room only areas on the 300 level are located at the back of the walkway which separates the lower rows from the upper rows