You define grading regions where grading requires different criteria along different parts of the footprint.
Where you need regions, you apply the criteria to only part of the footprint rather than the entire footprint.
For example, you might have a grading region with a slope of 3:1, and another region with a slope of 2:1, separated by a transition region, in which the grading merges from 3:1 to 2:1. Regions to which criteria have been applied are called control regions.
You are prompted to create a transition region if you specify the start point of a grading region to begin within an existing grading on the same footprint. You can also insert transition regions by using the Grading Creation Tools.