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 6240-01-246-3248
NSN 6620-01-175-3429
NSN 5985-01-520-3113
NSN 2925-00-643-4243
NSN 6220-01-648-2184
NSN 6150-00-250-3059
NSN 6620-01-421-3917
NSN 5835-01-063-6284
NSN 6150-00-857-6896
NSN 6320-01-429-9871
NSN 6685-01-205-7207
NSN 4140-01-543-0645