A rigid item designed to frame a structural opening for reinforcement purposes and/or to accommodate covers, access (as modified) and doors, access (as modified).
NSN 6220-01-327-3272
NSN 6650-01-409-1992
NSN 6145-00-427-7201
NSN 4140-01-462-2487
NSN 5855-00-281-3843
NSN 5996-00-270-0340
NSN 6685-01-453-7894
NSN 6240-01-495-1912
NSN 5975-01-064-5190
NSN 5985-00-538-0611
NSN 5930-01-423-8646
NSN 5925-01-518-2503