Autodesk AUTOCAD 2006 Command Reference Manual page 536

Ignore
IIgnores all internal objects and hatches or fills through them. You can also
set the Ignore style by adding ,I to the pattern name in the HPNAME system
variable.
Outer
Hatches or fills inward from the outer boundary. HATCH turns hatching
or filling off if it encounters an internal island. This option hatches or fills
only the outermost level of the structure and leaves the internal structure
blank. You can also set the Outer style by adding ,O to the pattern name
in the HPNAME system variable.
Normal
Hatches or fills inward from the outer boundary. If HATCH encounters an
internal island, it turns off hatching or filling until it encounters another
island within the island. You can also set the Normal style by adding ,N to
the pattern name in the HPNAME system variable.
512 | Chapter 10