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 5975-01-439-8105
NSN 5925-01-064-2388
NSN 5945-01-441-2854
NSN 6650-00-610-3956
NSN 5998-01-200-7207
NSN 4140-01-452-7422
NSN 6610-01-012-4081
NSN 5990-01-217-1550
NSN 4140-01-480-9575
NSN 6145-01-599-9935
NSN 5985-00-064-6416
NSN 2925-00-163-9016