The cover plate, surround plate, and seat ring of manhole covers are typically made of hot-rolled carbon steel or the same material as the hull structure where the manhole cover is installed.
Heat rings and handles are made of ordinary carbon steel; sealing heat rings are made of flame-retardant rubber or seawater (freshwater) resistant rubber; bolts or studs are made of stainless steel or carbon steel; nuts are made of carbon steel, stainless steel, or brass, etc.
Bolts, studs, nuts, and washers made of carbon steel should all be galvanized.
