What was found
AIRCRAFT IN BASE MAINTENANCE. CORROSION OF INTERCOSTAL AT FASTENER HOLES UNDER FLOOR PANEL BETWEEN STA 951 AND STA 967 AT LBL 20, MEASURING L=2.5 IN, W=2.0 IN, D=0.027 IN. REPLACED INTERCOSTAL WITH NEW, IAW DRAWING 147A5660 AND B737NG SRM 51-40-10-2R. SUPPLEMENTAL INFORMATION. INITIAL REPORT IDENTIFIED AS A LEVEL 2 FINDING IN ERROR, REPORT CORRECTED TO REFLECT PROPER LEVEL.