Why most manhole covers are not square or rectangular

Answer: The reason why these manhole covers are round is actually very simple, round manhole covers are not very different in size, including diameter, round manhole covers are easy to manufacture and take up less space, and can ensure a good seal at any position. In addition, it is easier and more accurate to manufacture round manhole covers than any other shape of cover. Finally, round manhole covers, once repaired and moved to a new position, require less effort and manpower to remove them, because of their shape, which allows them to be easily pushed out.