Street manhole cover, has matching frame and base ring raised via matching bolts to adapt to upper edge of street, where liquid tar is filled in raised space between base ring and frame having retaining ring at its lower edge

摘要

The cover has a matching frame and a base ring that are connected to each other through matching bolts. The frame includes a retaining ring at its lower edge. The frame and the base ring are raised through the bolts to adapt to an upper edge of a street. Liquid tar e.g. bitumen, is filled in a raised space between the base ring and the frame.