A chimney cap is a protective cover that is installed on the top of a chimney to prevent rainwater, debris, and animals from entering the chimney. It is typically made of metal, such as stainless steel or copper, and comes in various shapes and sizes to fit different types of chimneys. Chimney caps are designed to keep rainwater out of the chimney, which can cause damage to the chimney flue liner, and in extreme cases, cause the chimney to collapse. The cap also prevents animals, such as birds, squirrels, and raccoons, from nesting inside the chimney, which can create a fire hazard and lead to blockages that can cause smoke to back up into the house.