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 5905-01-181-8957
NSN 4140-00-269-5795
NSN 5855-01-607-6521
NSN 5935-01-117-5629
NSN 5915-01-443-6559
NSN 6145-00-088-3766
NSN 5960-00-703-3208
NSN 5910-00-096-7611
NSN 5998-01-238-9370
NSN 6240-00-964-3728
NSN 5996-00-202-6576
NSN 7035-01-209-6325