All goods must first be classified by reference to a heading number, the first four digits of a commodity code. Rule 1 provides that a good is classified according to its main heading section or chapter heading, where a heading doesn't require further definition. Explanatory notes before the start of each chapter provide additional clarification for the meanings of headings within a chapter. Most goods are classified using this rule, as the heading classification is self-evident and doesn't need any further reference to any of the other rules.
Goods can be classified using a heading falling under Rule 1. For example a live horse has the main heading number 01.01 and is considered not to need any further definition under the interpretive rules. Looked at another way, in chapter 31 of the Tariff, the notes provide that certain headings relate only to certain goods.
If your goods cannot be classified solely by using rule 1 you should move through the provisions of rules sequentially - if a rule doesn't provide guidance, move on to the next rule and so on.
The rules have legal status and form the basis for correctly classifying your goods.