Knurling is a common surface treatment applied to CNC machined metal parts, primarily for enhancing grip and aesthetic appeal. Often seen on knobs, handles, and fasteners, knurled patterns improve tactile performance and can also serve functional purposes such as press-fit retention or torque transfer. This article outlines the main types of knurling, their applications, cost and processing difficulty comparison, technical drawing standards, selection of knurling pitch or modulus, and commonly used manufacturing methods.