Pilu Hall is an important (undated) building at Xiangyan Temple in Liulin county, Shanxi province. The timber-framed structure appears clear and simple, but there are some contradictions and inconsistencies in its design. Based on data acquired via 3D laser scanning and manual measurement, this paper restores the proportional design of the timber frame and interprets the column layout, the beam framework, and the (caifen) unit-based modular system. The authors suggest that two types of construction rulers were used at Pilu Hall; one measuring 310 mm in length and the other one, 318-319 mm. The existence of two rulers reflects the complex issue of determining the construction date. Most likely, Pilu Hall was built in the Yuan dynasty; it was repaired in the Ming and Qing dynasties, but its dougong retained the original (Yuan) dimensions and structural characteristics.