My first-ever design took me quite a bit of time. It's not perfect, but I'm happy with it. I wanted to do something that hadn't really been done before. So I present to you the manhole cover. I work in the field, and these are the covers you see on the road or sidewalks. They are usually 29 inches in diameter and made out of cast iron. Of course, you can scale this to your liking, and you can even split it into multiple files to create one of the original size. Or just scale them down for a nice little coaster.