What is a cover board (chimney)

The chimney cover plates are made of cast reinforced concrete and serve to cover the space between the chimney liner and the brick chimney at its mouth. They have the necessary strength and resistance to external influences. The underside of the board has a gutter groove. According to the shape of the insert, the holes are square or round. Each hole has a concrete collar that prevents rainwater from flowing. 

Cover plates are divided into single pass, two or three passes. You can also make custom made atypical covers. 
To the chimney, the cover plate is bolted with anchor bolts. It installs on the last pipe and moves to the crossing.  It must contain a rainbow cuff to protect it from rainwater.