Generate a plot with filled areas. The plot requests are ordered to draw the lowest plot first. Area 1 occupies the space between the lowest (first) plot line and the horizontal axis, and area 2 is below the highest (second) plot line. This arrangement prevents the pattern for area 1 from overlaying the pattern for area 2. AREAS=2 fills all the areas below the second plot line.
proc gplot data=stocks; plot low*year high*year / overlay haxis=axis1 hminor=4 vaxis=axis2 vminor=1 caxis=black areas=2; run; quit;