On the operational level, and then picking up wood (IFS) of the vertical Center line along to be performed to determine the height of a horizontal configuration level.
The operation will take the class and then picking up the timber (IFS) of the Appalachian Center line along the way to be used in determining the height of the line to the next level.
In practice the level value and collect value taking middle (IFS) of the Center line simultaneously to used in determination of the height of the determination of the next level.