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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.

 SYMBOL VERBALDESCRIPTION TYPE of TOLERANCE TYPE of FEATURE NOTES 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