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 5998-00-079-0036
NSN 5996-01-508-2467
NSN 6610-01-329-2289
NSN 5920-01-461-6141
NSN 6220-01-433-9502
NSN 4140-00-560-8166
NSN 6645-00-153-3834
NSN 6130-01-514-3938
NSN 5910-01-015-1945
NSN 6220-01-281-0349
NSN 5945-01-384-9780
NSN 6610-01-160-8815