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 6610-00-107-1944
NSN 6650-01-350-2515
NSN 5915-00-246-0596
NSN 5985-01-630-7003
NSN 5965-01-089-8579
NSN 5855-00-167-7893
NSN 5996-00-583-9498
NSN 5990-00-254-4825
NSN 5915-01-101-0817
NSN 6220-01-273-7424
NSN 6320-01-123-6814
NSN 6685-01-200-1793