282 Geometric Dimensioning and Tolerancing Copyright Goodheart-Willcox Co., Inc. Orientation tolerances are total. This means that when applied to a surface, all ele- ments of the related surface must fall within the specified tolerance zone. When less demanding requirements controlling only individual line elements of a surface meet the design goal, then a note such as EACH ELEMENT appears below the associated feature control frame. This application permits individual line elements of a surface, rather than the total surface, to be controlled in relation to a datum. Parallelism, perpendicularity, and angularity, when applied to a planar surface, also control flatness to the extent of the orientation tolerance specified in the feature control frame. Orientation tolerances applied to features of size imply RFS. Therefore, MMC or LMC must be specified if any application other than RFS is intended. Parallelism specifies a tolerance zone oriented at a basic 0° angle from the datum plane or datum axis. Perpendicularity specifies a tolerance zone oriented at a basic 90° angle from the datum plane or datum axis. When using angularity, a basic angle must be specified to orient the tolerance zone from the datum plane or datum axis. As an alternate practice, an angularity tolerance can be used to control perpendicular and parallel relationships. Parallelism Tolerance Parallelism is the condition of a surface or center plane in which all points are equidis- tant from a datum plane. Parallelism is also the condition of an axis in which all points along its length are equidistant from a datum plane or datum axis. A parallelism tol- erance specifies a tolerance zone formed by two parallel planes or parallel lines, or a cylindrical tolerance zone, oriented parallel (basic 0°) to a datum and within which the controlled surface, axis, or center plane of the feature must lie. Example 7-1 details the parallelism geometric characteristic symbol and associated feature control frame. H = Letter height Symbol Specifications 1.5H 0.6H H 2H 60° Goodheart-Willcox Publisher Example 7-1. A feature control frame with the parallelism geometric characteristic symbol.