Pimenov, R. R. Lineup markup as an introduction to group theory. (Russian. English summary) Zbl 1429.97001 Vestn. Syktyvkar. Univ., Ser. 1, Mat. Mekh. Inform. 30, No. 1, 16-26 (2019). Summary: The article reveals the relationship between the ruler markup, the group of permutations of the three elements, involutive transformations and linear fractional functions. Threefold symmetry is shown, without which the ruler marking would be impossible. Examples and tasks useful for teaching mathematics at school and university are given. MSC: 97H40 Groups, rings, fields (educational aspects) Keywords:lineup markup, symmetry, group theory, involution, education PDFBibTeX XMLCite \textit{R. R. Pimenov}, Vestn. Syktyvkar. Univ., Ser. 1, Mat. Mekh. Inform. 30, No. 1, 16--26 (2019; Zbl 1429.97001)