Valid ordinal scales require deciding level count, midpoint, and category spacing

Evidence

If one is going to use or create an ordinal scale it is worth considering (1) the number of levels, (2) what the conceptual middle 0.50 level is, and (3) whether some categories are semantically closer together than others. — Gary Goertz, Social Science Concepts and Measurement, 808

Categorization

• APHORISMS: Reads as compact, reusable design advice for anyone building a rating scale or index.
• SEED: Angle: a practical checklist essay on constructing measurement instruments, contrasting the Goertz three-point rule with ad hoc scales.