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 6610-00-600-9417
NSN 2925-01-457-5649
NSN 5920-01-461-3214
NSN 5945-01-007-6808
NSN 6610-01-416-0652
NSN 5950-00-364-8162
NSN 5910-00-203-3736
NSN 5950-01-358-0363
NSN 6145-01-232-2658
NSN 5935-01-467-7511
NSN 5920-00-221-6439
NSN 4140-01-116-3138