As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCN - C21 CK - C - FLOORBEAM BS 986.5, LBL 44 TO RBL 49 HAS CORROSION IN SEVERAL PLACES ON UPPER FLANGE. MAINTENANCE REMOVED THE FLOORBEAM UPPER CAP FROM LBL 44 TO RBL 49 AND FABRICATED NEW UPPER CAP SECTION AND INSTALLED IAW B737 SRM 53-10-9 FIG 2 PG 7 - 11.