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The investigated factory-roof (F-R) patterns were produced by cyclictorsion loading of V-notched cylindrical specimens made of the high-strength low-alloysteel. A three-dimensional model of the F-R pattern was constructed by means of thestereophotogrammetry. This allowed us to recognize the geometrical proportions aswell as to understand the basic geometrical rules of its formation. The theoreticalanalysis revealed that the F-R initiates by elementary mode I branches at the front ofsemi-elliptical surface cracks. The exact positions of such branches can be analyticallydetermined in terms of the maximum synergy of mode II and mode III loadings. Anincreasing density of semi-elliptical cracks initiated on the surface results in therefinement and the size reduction of F-R patterns. This effect can, together with strongwear damage, explain the fact that the F-R patterns are usually not observed in the low-cycle fatigue region.