GRAPH:filling:hatch_patterns
A hatch pattern is composed of an angle and one to ten spacings.
These spacings are simply cycled through as the region is being
filled, that is, a line is drawn inside the region at the specified
angle, then a parallel line is drawn at the first spacing, then
another parallel line is drawn at the second spacing, and so on for
the number of spacings in that pattern. This process is repeated
until the region is filled. The hatch patterns can be redefined
with the SET HATCH command and displayed with the DISPLAY FILL
command. There are ten hatch patterns available.