Security guards / Security guards

City manhole covers are moved,theft and damaged frequently.And no timely maintenance. It lead to pedestrians, animals and vehicles to fall in the well easily.It is a huge threat to the safety of life and property.
A layer of rare earth luminescent materials embedded in the groove around the edge of the cover and the base.When the covers get moved, lost or damaged,red will be illuminated from the cover edge to remind people to avoid the danger.