#notch.indentation  a V-shaped or U-shaped indentation carved or scratched into a surface; "there were four notches in the handle of his revolver"
  supertype:  #indentation.concave_shape  a concave shape in a surface or edge or coastline etc.
  subtype:  #serration  a single notch in a row of notches; "one of the serrations was broken off"
     subtype:  #sawtooth  a serration on a saw blade
  subtype:  #thumb_index__thumbindex  one of a series of rounded notches in the fore edge of a book to indicate sections

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