LOOP AT <fs_item> INTO <fs_item_line>.
Assign component 'KEY' of structure <fs_item_line> to <comp>.
READ TABLE <fs_header> ASSIGNING<fs_header_line> with key = <comp>.
LOOP AT <fs_item> INTO <fs_item_line>.
Assign component 'KEY' of structure <fs_item_line> to <comp>.
READ TABLE <fs_header> ASSIGNING<fs_header_line> with key = <comp>.