SYMBOLSET
SYMBOL
  NAME "horizline"
  TYPE VECTOR
  POINTS
     0 0
     1 0
  END # points
END # symbol
SYMBOL
  NAME "arrowhead"
  TYPE vector
  FILLED true
  #ANCHORPOINT 0 0.5
  POINTS
    0 2
    4 1
    0 0
  END # points
END # symbol
SYMBOL
  NAME "arrowtail"
  TYPE vector
  FILLED true
  ANCHORPOINT 1 0.5 # to shift the arrowtail
  POINTS
    0 2
    4 1
    0 0
    -99 -99
    0 1
    4 1
  END # points
END # symbol
END