The article is devoted to the concept of a rule as a tool of scientific and orthological description. A rule is a conventional kind of scientific interpretation in any writing system, such as the description of morphological types in morphology or syntactic models in syntax. In this regard, rules must comply with the requirements for tools of scientific and orthological description. A rule as a tool for scientific description should be internally consistent and not contradict other rules, clearly define the described range of phenomena, cover all cases, clearly distinguish between the scope of the rule and the scope of the dictionary, be terminologically correct. As an orthological tool, a rule should not only correspond to the modern norm, but also determine the vector for future codifications. As a modern orthological tool, a rule should be accompanied by a commentary. The purpose of this commentary is to show the reader the scientific and methodological validity of both a general approach to describing the problems of different sections of the spelling, and each specific rule, to present a range of different interpretations of a particular spelling and justify the proposed one. The proposed description is based on the authors’ theoretical views on writing as a self-developing system and on the role of codifiers as a subjective factor in the development of this system. The conclusions are based on studies of historical changes in each spelling rule and writing in general, as well as modern fluctuations observed in spelling practice and directions for their elimination. This article reveals the authors’ approach to creating a commented set of rules for Russian spelling – a complete, consistent, scientific description of writing in the common form of rules that meets modern standards.