If square, due to the diagonals being significantly longer than each side, such a manhole cover can easily fall into the well along the diagonal direction of the well opening, posing a safety hazard. If the well opening is circular or notably smaller than the cover, the square cover won't fall into the well. This involves the issue of material utilization and conservation. The use of the cover depends on the size of the well opening. If a square cover much larger than the well opening is installed, the material utilization and practical value are naturally less efficient than using a circular cover directly, which saves the material for the cover and ensures the safety of the well opening.

In rural areas and cable wells, square designs are generally used to better prevent the entry of rainwater and other liquids.