Every one of us has seen manholes – these are the round openings which connect the sewerage pipes of our city or village. However they serve a much higher purpose – manholes are used as an entry point for pipe cleaning. Each manhole is covered with a round cover in order to prevent accidents.

So why round? Why not rectangular or triangular? The answer is pretty simple – covers with another shape would easily fall through the opening, because of their varying size. That is not the case with circular manhole covers – each of the covers has the same diameter and it is never changed. This way the covers are able to last for longer and withstand the street traffic running over them daily.

Manhole covers are made with a small sized lip on which they rest. This way they are much steadier and well sealed. The last advantage of circular manhole covers is the fact they are easier to transport – they require less manpower, because they can easily be rolled instead of carried.