Marker for manhole covers with ventilation openings

摘要

A marker stopper (3) possessing a marked upper surface (4) is pressed or screwed into the ventilation openings (1) in the manhole cover (2). The stopper is in the form of a cup with at least its base (5) made of transparent material. The marking is on the base inside the cup and faces the outside of the cup's base and the marker is on a support (8) placed inside the cup. A gas-tight cover plate or disc (7) is applied to the underside of the marker, or that of the marker-holder. The marker has cavities for prefabricated marker symbols.