SUBROUTINE  PLTKB (Z1,ZE,Z2,NZ,NX,NY,PL)

C     [CONTOUR BORDER]
C     ZE(NX,NY)  ARRAY FROM WHICH BORDER VALUES ARE TAKEN
C     (Z1,Z2)    INTERVAL DEFINING SCALE
C     NZ         NUMBER OF Z-INTERVALS TO BE MARKED
C     PL         PEN MOVEMENT SUBROUTINE, PERHAPS PLTCA
C     [05-JAN-75]

      EXTERNAL    PL
      DIMENSION   ZE(1)
      DATA        EP/0.01/

      IX(I,J)=I+NX*(J-1)

      DX=1.0/FLOAT(NX-1)
      DY=1.0/FLOAT(NY-1)
      DZ=(Z2-Z1)/FLOAT(NZ-1)
      Z=Z1
      DO 50 K=1,NZ
      FK=FLOAT(K)
      X=-HX+DX
      Y=-HY+FK*EP
      CALL PL (X-DX,Y,.FALSE.)
      DO 10 I=2,NX
      I1=IX(I-1,1)
      I2=IX(I,1)
      CALL PLTIL (X-DX,Y,ZE(I1)-Z,X,Y,ZE(I2)-Z,PL)
   10 X=X+DX
      X=HX-FK*EP
      Y=-HY+DY
      CALL PL (X,Y-DY,.FALSE.)
      DO 20 I=2,NY
      I1=IX(NX,I-1)
      I2=IX(NX,I)
      CALL PLTIL (X,Y-DY,ZE(I1)-Z,X,Y,ZE(I2)-Z,PL)
   20 Y=Y+DY
      X=HX
      Y=HY-FK*EP
      CALL PL (X,Y,.FALSE.)
      DO 30 I=2,NX
      I1=IX(NX-I+2,NY)
      I2=IX(NX-I+1,NY)
      CALL PLTIL (X,Y,ZE(I1)-Z,X-DX,Y,ZE(I2)-Z,PL)
   30 X=X-DX
      X=-HX+FK*EP
      Y=HY
      CALL PL (X,Y,.FALSE.)
      DO 40 I=2,NY
      I1=IX(1,NY-I+2)
      I2=IX(1,NY-I+1)
      CALL PLTIL (X,Y,ZE(I1)-Z,X,Y-DY,ZE(I2)-Z,PL)
   40 Y=Y-DY
   50 Z=Z+DZ
      RETURN

      END