This guide outlines a standardized way to measure and report on the light-related features of skylights and tubular daylighting devices. It details the steps and precautions for obtaining consistent measurements of these devices with glass or plastic panels. The guide specifies the needed tools and method for measuring these devices accurately. It also covers the equipment calibration, determining sun angles, and assessing sky conditions. The document focuses on achieving uniform and repeatable measurements for these daylighting products.