Rule 5 covers the packaging within which the goods to be classified are contained.
Rule 5, part a - cases, boxes and similar containers
Part a deals with the classification of cases, boxes, and similar containers, which are specially shaped or fitted to contain the item. The case must be designed to have similar durability to the good they're protecting, rather than being simple packaging.
Some examples of this rule are:
musical instrument boxes, bags or cases - the heading would be the instrument they contain - 'stringed instruments, guitars, violins, harps (92.02)'
jewellery boxes containing a piece of jewellery - the heading would be 'articles of jewellery and parts thereof (71.13)'
electric shaver cases - the heading would be 'shavers and hair clippers and hair removing appliances (85.10)'
Cases can be imported or exported with the articles they're designed to contain. In most instances, the case will be classified along with the item contained.
Rule 5, part b - packing materials and packing containers
Part b is concerned with packing materials. As with cases in part a, the material is generally classified along with the articles they're packing. The packing must be clearly specific to the goods, but may be suitable for repetitive use.
For example metal drums, rare gases and other non-metals (28.04)'.