They are combination structures made up of solid, and shell structures.
Explanation:
Thinking of a lunch pack which is shaped as a solid bag made up of different compartments to hold food, what comes to mind are;
1. The solid structure: This is seen in the form of the bag which has solid makeup.
2. The shell structure: This is seen in the different compartments holding the different types of foods. Shell structures are usually in the form of containers made to hold something in.
