It would be a ring with a stick through it. In a 2D slice down the middle, it would look like a donut with a circle (the slice of the stick) in the hole. The

It would be a ring with a stick through it. In a 2D slice down the middle, it would look like a donut with a circle (the slice of the stick) in the hole. The circle appears to be stuck inside it, with no way out in 2D. In 3D, you just pull the stick out of the ring.