(1) Use of markers. Markers should be used to mark obstructions when it has been determined that it is impracticable to mark such obstructions by use of surface colors, or it has been determined that markers should be used to provide protection for aeronautics in addition to that provided by the application of aviation surface orange and white colors.

(2) General application. Markers used to mark obstructions should be displayed on or adjacent to the obstruction in conspicuous positions so as to retain the general definition of the obstruction. The size of such marker shall be a visible surface from all directions not less than that of a 36 inch sphere the length of which shall not exceed twice its median width: Provided, however, That the commission may approve a nonconforming marker.

(3) Shape. The shape of such markers should be distinctive to the extent necessary to insure that they are not mistaken for markers employed to convey other information, and they should be such that the hazard presented by the obstruction they mark is not increased.