Geometric dimensioning and tolerancing (GD&T) is a way to document the exact size and shape of a part. It is used to make sure that parts and assemblies fit together, and to make sure that parts made by different people and on different machines will still fit together. GD&T uses symbols to describe the size and shape of a part, and how it should fit together with other parts. These symbols are like shortcuts that help save time and money when designing and building products.