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Symbol Glossary
What follows is a short summary of feature control symbols used in GDT. As was mentioned in the introduction, this is not intended to be an exhaustive presentation of GDT, but rather a concise, clear explanation of GDT's most important yet often misunderstood points. Therefore, we do not explain in detail all of the symbols listed below.

In the "Type of Feature" column, "Individual" means that this type of tolerance does not need to be referred to a datum. Individual GDT tolerances are the easiest to understand for a beginning GDT user. "Related" designates a type of tolerance that must be referred to a datum. "Individual or Related" can be of either type, depending on the situation.

Position Location Related Commonly used.
Concentricity Location Related Difficult to inspect.
Circular Runout Runout Related
Total Runout Runout Related Includes Circular Runout
Perpendicularity Orientation Related
Parallelism Orientation Related
Angularity Orientation Related
Profile of a Surface Profile Individual or Related
Profile of a Line Profile Individual or Related
Flatness Form Individual
Straightness Form Individual
Roundness or Circularity Form Individual
Cylindricity Form Individual