The heavy frame is an essential component of manhole infrastructure, made from high-quality steel or cast iron, encased in concrete to ensure stability and durability. It serves as part of the manhole cover, which is typically placed on the manhole body, often embedded in a solid concrete base. The heavy cover, typically rectangular in shape, is inserted into the heavy frame, creating a complete structure.

A distinguishing feature between the heavy frame and its lighter counterparts is the rounded corners, imparting a robust appearance and providing additional strength. Currently, heavy frames made of steel are most commonly used due to economic considerations, offering adequate strength and durability while remaining cost-effective.

The B125 load class of the heavy frame indicates its theoretical capacity to withstand a static load of 12.5 tons. In practice, this means that such a frame can be applied, for instance, in car parks for both passenger and delivery vehicles, providing reliable support for users and ensuring longevity over many years of use.