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 4140-01-456-3899
NSN 5960-01-413-3877
NSN 5985-00-334-8160
NSN 5990-01-588-3999
NSN 5975-01-146-6395
NSN 5925-00-111-1748
NSN 5985-01-534-1155
NSN 5998-00-570-7328
NSN 5945-00-862-3979
NSN 5950-01-297-0829
NSN 5915-00-438-9562
NSN 5999-00-550-8059