The ASTM D4138-2007A standard provides implementing procedures for the measurement of dry-film thickness of protective coating systems by microscope observation of precise angular cuts. Three measurement procedures are included: using a grooved cutting tool (Procedure A), a ground tool (Procedure B), and a drill tool (Procedure C). Suitable for hard substrates, not for soft or ductile substrates that may deform during cutting. The measurement range is typically 2 to 2000 microns, depending on the blade cutting angle. The standard emphasizes the importance of dry-film thickness for coating performance and notes safety and health responsibilities for operation.