Tools > Alignment > To Plane makes one plane of an object perpendicular to an axis of the world coordinate system. You specify a plane on the object by clicking three points, and an axis of the world coordinate system by selecting X, Y, or Z in the dialog, and click Apply.
Before using this function, it is useful to make the world coordinate system visible by checking Display Manager > Accessories > World Axes.
The controls are:
Define Plane group - specifies which of three points is the next to be clicked on the object. A set of three points defines the plane.
First Point radio button - the next point that you click in the Viewing Area is the first of three points that define a plane.
Second Point radio button - the next point that you click in the Viewing Area is the second of three points that define a plane.
Third Point radio button - the next point that you click in the Viewing Area is the third of three points that define a plane.
Orientation group - controls the relationship of the defined plane to a world axis and the relationship of the object to the defined plane
Perpendicular to (X Axis, Y Axis, Z Axis) - specifies the world axis to which the defined plane will be made perpendicular.
Turn Around checkbox - flips the object 180 degrees about the “Perpendicular to” axis.
OK button - closes the dialog with the object in its rotated position.
Cancel button - restores the object to its condition before starting this function, and closes the dialog.
Apply button - rotates the object to make a selected plane perpendicular to a selected world axis, and leaves the dialog open for additional rotation.