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 6610-01-539-0014
NSN 6610-01-274-2479
NSN 6620-01-103-7508
NSN 5935-01-101-3383
NSN 6220-01-579-6112
NSN 6240-01-399-8573
NSN 5990-01-612-5323
NSN 6320-00-139-1090
NSN 6645-01-633-1852
NSN 5935-01-271-4780
NSN 5975-01-548-0886
NSN 5905-00-284-6188