What material is commonly used for man hole covers?

Manhole covers are predominantly made from cast iron due to its strength, durability, and ability to withstand heavy loads, such as those from vehicles and pedestrians. The choice of cast iron also provides resistance to corrosion and environmental wear, making it suitable for use in various weather conditions.

Concrete is sometimes used for specific applications, but it's less common for standard manhole covers because it may not have the same load-bearing capabilities and can be more prone to cracking over time.

Plastic and wood are generally not suitable materials for manhole covers. Plastic lacks the necessary strength to support heavy loads, and wood is not durable against the elements or the weight of traffic. The term "ironic shapes," which appears to be a play on words, does not refer to a recognized material used for manhole covers and does not align with standard engineering practices.

Therefore, cast iron is the preferred material, making it the right choice for ensuring safety and functionality in urban infrastructure.