ASTM D7438-20 is a standard practice developed by the American Society for Testing and Materials (ASTM) that specifies the method of field calibrating and application of handheld moisture meters under end-use conditions. The standard applies to the measurement of the water content of solid wood and its articles, including wood containing additives, and is designed to improve the accuracy and Reliability of measurements through calibrating. The standard details the calibrating process, conditions of use, and how to perform readings correction based on wood characteristics (e.g., texture, growth ring orientation) and environmental conditions (e.g., Humidity layer). In addition, it emphasizes that moisture meters of different technologies may not provide equivalent readings under the same conditions, so they need to be calibrated according to ASTM D4444. This standard provides a scientific basis for wood processing and quality control to ensure the effectiveness of handheld moisture meters in practical applications.