Thinking of building a backyard firepit this spring to replace my old, worn firebowl. I want to keep it simple and cheap. Don't want to buy one of those pricey kits. I was planning to just get a bunch of pavers, set 'em up and throw some gravel down inside. Here's my question: How important is a metal ring? I see those are part of the kits, but they seem somewhat dubious to me. Is one really needed to protect the pavers from the heat?