Sewer Cover Plates are a vital component of the sewer system. They are used to cover the top of a manhole and protect it from damage. It is usually made of cast iron, concrete, or plastic. Cast iron ensures the sewer cover`s longevity. Cast iron is a lot more durable than other metals, and it can withstand a lot of wear and tear. It’s also fairly easy to maintain and has the ability to be recycled.