These are the 3D shapes that I know..
A SPHERE
A CYLINDER
A CUBE
AND A CONE!

The verses go over different "real-life" objects that could be each of those 3D shapes; On the cone verse, I would suggest pointing out ahead of time (or perhaps after the first intro of this song) how the nail is more easily identified as a cone if you kind of "chop off" the tip of it and examine it that way...