Parallelism tolerance of a line to a reference systemThe extracted centre (actual) line must lie between two parallel planes at a distance of 0.1 or 0.2 that are parallel to reference axis A. The direction of the width of the tolerance zones relative to reference plane B is specified by the direction of the leader lines and the secondary reference (2D) or orientation plane (3D).644 The extracted centre (actual) line must lie between two parallel planes at a distance of 0.1 or 0.2 that are parallel to reference axis A. The orientation of the tolerance zones relative to reference plane B is specified by the orientation plane.The limitation planes of tolerance zone - 0.2 are perpendicular to B - 0.1 are parallel to B