Geometric Dimensioning and Tolerancing : Every Mechanical design engineer, machinists and QA engineer needs to understand the modern global language of Engineering Design. Among other modern practices, the knowledge of GD&T is considered to be a must for every mechanical engineer wanting to work in the global engineering platform. Geometric Dimensioning & Tolerancing (GD&T) is the modern standard of design. The GD&T standards for drawing and designing are published by the American Society of Mechanical Engineers (ASME Y14.5) and ISO.