Titre
Please share those informations... but do not forget to add a link to spontex!
Manholes
By mansuetus on 2008-12-01 02:00:00   


Manhole covers are round so that they cannot fall in the opening.

Details :

The hole in the middle is for opening them with a metallic bar.
Some other covers are square (like the ones for underground phone cables) and could fall.

Sources :

Wikipedia – Manhole