A metallic item placed in a manhole to seat the frame, manhole.
NSN 6650-01-259-8452
NSN 5985-01-268-1359
NSN 5975-01-141-3923
NSN 5996-00-258-4954
NSN 5895-00-812-6181
NSN 5999-00-243-6500
NSN 6645-00-276-7544
NSN 5895-01-386-7140
NSN 5950-01-461-5205
NSN 6620-01-258-7005
NSN 5996-01-270-0299
NSN 6650-00-098-6128