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 5998-00-770-5229
NSN 6685-00-144-6362
NSN 6645-01-304-0889
NSN 4140-01-250-0980
NSN 6220-01-435-4839
NSN 6610-00-244-2816
NSN 5960-01-144-0354
NSN 6135-01-471-7325
NSN 5985-00-244-5147
NSN 5960-01-202-6610
NSN 5945-01-463-2802
NSN 5998-01-421-7911