Symmetry - The condition where the median points of all opposed elements of two or more feature surfaces are congruent with the axis or centerplane of a datum feature.
Symmetry Control - A geometric tolerance that limits the symmetry error of a part feature.
Tertiary Datum - The third datum plane that the part contacts in a dimensional measurement.
3-2-1 Rule - Defines the minimum number of points of contact required for a part datum feature with its primary, secondary, and tertiary datum planes.
Tolerance - The total amount that features of the part are permitted to vary from the specified dimension.
Tolerance Analysis Chart - A means of graphically displaying the limits of a part as defined by the print specifications
Tolerance of Position Control - A geometric tolerance that defines the location tolerance of a feature of size from its true position.
Tolerance Stack - A calculation used to find the extreme max. or min. distance on a part.