# Choosing Orientation and Handedness

You specify the location of an affine rectangle to determine what portion of the input image is included within the rectangle. Affine rectangles that occupy the same part of an image can have their vertex points in different locations.

The orientation and handedness of an affine rectangle determine how the affine rectangle is used. The Caliper tool will use the Po-Py axis of the affine rectangle as the projection direction and the Po-Px axis as the search direction.