The manufacturer’s manhole covers are made of metal or plastic (composite materials) , and their shapes are square , round , or rectangular .
No colored or gilded covers by this manufacturer have been found. City emblems also do not appear on the manufacturer’s covers.
In many cases, the function of the cover is unknown, except for covers intended for traffic light control or drainage covers .
The year of manufacture usually does not appear on the cover.
Standards The European standard EN124 and its corresponding load classes appear on many covers, with the most common load classes being B125 and A15 . The international SGS standard can also be found .
Typical Covers There are two main types of covers: one with a background of two circles in the center (usually for traffic light controls) , and another with a background featuring a geometric shape resembling a bridge and a wide diagonal stripe in the center . In addition, there are also drainage covers .