Parsons recommended a method of automatic machine control that would guide a milling cutter to produce a "thru-axis curve" in order to generate smooth profiles on work pieces.

By properly setting the coordinate axis, the discrete data of a symmetric coupler curve are made to satisfy the conjugate symmetry.

The middle wing is twisted back to the intersection like a motorcycle entering a curve at the highest speed with an axis pointing out to Nong Prajak park, Udonthani's important public park.