#vertical_surface  a surface that is vertical
  supertype:  #surface  the outer boundary of an artifact or a material layer constituting or resembling such a boundary; "there is a special cleaner for these surfaces"; "the cloth had a pattern of red dots on a white surface"
  subtype:  #face.vertical_surface  a vertical surface of a building or cliff
     subtype:  #perpendicular  an extremely steep face
     subtype:  #coalface  the part of a coal seam that is being cut

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