The manhole covers in Thermi are made of metal and come in square , rectangular , or circular shapes.

In most cases, it is not known who the intended consumers of the covers are, and therefore the specific purpose of each cover is also generally unclear. In a few cases, the name of the consumer ΔΕΥΑ appears (even then, the purpose of the cover remains uncertain), or the purpose can be inferred from the cover itself (for example: drainage slots) .

The city emblem does not appear on the covers.

In most cases, the covers are not particularly distinctive and usually feature a background pattern of squares , diamonds , or an X-shaped design .

Manufacturers
Most of the covers were made by Greek manufacturers: A. Stylianidis , M. Ioannidis , Misailides Brothers . The site also includes a cover produced by the international manufacturer PAm .

Standards
The European standard EN124 and its related load classes (A15–D400) frequently appear on the covers. Other international standards have also been found.