In the metaphorical sense, the shell might be a "carry-on" bag on wheels, stuffed full of cables, discs, dongles, batteries, plugs and paper documents (just in case of disc failure).

And he gave a very good analogy in saying, "it was almost as incredible as if you'd fired a 15 inch shell at a piece of tissue paper, and it came back and hit you."

May: There are also some fine art crafts, including wood carving, shell ornaments and paper-cut.