Measuring With Datums: Orientation Tolerance

Orientation tolerance is a geometric tolerance that determines the orientation for the form in relation to a reference.
The parallelism, perpendicularity, and angularity of two lines or two planes are measured using a datum plane as a reference. This can also be measured using a height gauge or square ruler.
Using a coordinate measuring machine, targets of a size difficult to measure with a height gauge or ruler, as well as positions that are difficult to measure with these tools, can be measured by taking advantage of the mobility of the stylus.