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 5975-01-394-4152
NSN 4140-00-839-4911
NSN 5835-01-268-1924
NSN 5930-01-561-2560
NSN 5960-00-457-1082
NSN 6220-01-373-2778
NSN 6150-01-184-5224
NSN 5920-01-190-0265
NSN 6135-01-350-2932
NSN 6110-00-450-6977
NSN 5990-00-223-5938
NSN 5935-01-634-0668