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 6150-00-490-6081
NSN 4140-01-189-7899
NSN 5945-01-527-3833
NSN 6645-00-619-8102
NSN 5935-01-391-5298
NSN 5999-01-147-5856
NSN 5915-01-564-5560
NSN 6135-00-044-3860
NSN 6650-01-556-6941
NSN 5985-00-905-0542
NSN 5920-01-052-9152
NSN 5999-00-519-5455