As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LT SIDE FUSELAGE INTERCOSTAL AT STR 21L FROM FS 319.70 TO FS 333.00 HAS CORROSION. C-CHECK RO 9/5/2020. REMOVED AND INSTALLED NEW BACK-UP SILL INTERCOSTAL AT STGR 21L FROM FS310.00 TO FS333.00, REF CRJ-700 SRM AND DRAWING. PRESSURIZATION LEAK CHECK GOOD. COMPLIED WITH TASKCARD.