Through the study of the “integer-number ruler” and the analysis of survey data based on a 3D point cloud model of the Hall of Great Perfection at the Confucius Temple in Jiading, this paper discusses the possible application of the technique known as “decrease in ruler unit for section design” to the roof slope of the hall. This technique was used to calculate the vertical distance between two roof purlins (from ridge to eaves purlin) in such a way that their magnitudes expressed in whole numbers were gradually decreasing from high to low. The paper then analyzes the construction logic and scope of application of this technique in the region around Jiading in order to extend the “integer-number ruler” study from the building span, building depth, and column height to the roof slope.