Orientation Tolerances: Parallelism, Perpendicularity, Angularity
Tilt, square, and angle - but not place
Parallelism, perpendicularity, and angularity control the orientation of a surface, axis, or center plane relative to one or more datums, and they always require a datum. The zone is two parallel planes at the stated separation, or a cylinder when the tolerance is applied to an axis and carries a diameter symbol. For angularity the angle must be a basic dimension; a toleranced angle combined with an angularity callout is a contradiction on the drawing.
Orientation tolerances constrain orientation and, within their zone, form: a surface controlled perpendicular to 0.1 must also be flat within 0.1. They do not locate. A perpendicularity callout on a hole says nothing about where the hole sits; position or profile is needed for that. This is the most common trap - a stem describing a hole that is square to the datum but in the wrong place calls for a locational control, not an orientation one.
Two further traps: an orientation tolerance looser than the locational tolerance on the same feature has no effect (its zone cannot escape the larger zone), and applying MMC to an orientation tolerance on a feature of size generates bonus tolerance and a virtual condition exactly as position does.
Worked example: perpendicularity 0.08 to datum A on a face means the face must lie between two parallel planes 0.08 apart whose orientation is exactly perpendicular to plane A. That band floats - only its tilt is fixed, not its height. The inspector orients a 0.08-wide zone square to A and confirms the whole surface fits inside it.