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 5930-01-251-4978
NSN 5835-01-495-5986
NSN 6110-01-654-1334
NSN 6110-01-513-2997
NSN 5930-01-430-3670
NSN 5835-00-148-6026
NSN 6320-01-092-4101
NSN 6240-01-523-2050
NSN 6145-01-134-0850
NSN 5910-01-237-1701
NSN 5910-00-830-6353
NSN 5895-01-403-2793