I have an old Chimney that is hooked up to a fireplace that has been long since bricked up. It's about 6 feet above roof level. I want to 'take it down' to about 6 inches. What is the cap on top called? I have been looking online and only found caps for functional chimney's. I need a 'concrete' cover to seal the chiney up completely. Or should I just make one myself?