You can fill existing objects or enclosed areas with hatch patterns, solid color
fills, or gradients, or you can create new hatch objects.

Choose from:

• Predefined hatch patterns. Choose from over 70 ANSI, ISO, and other industry-standard hatch patterns, or add
  hatch pattern libraries supplied by other companies.
• User-defined hatch patterns. Define your own hatch patterns based on the current linetype, with spacing, angle,
  color, and other properties you specify.
• Custom hatch patterns. Hatch patterns are defined in the acad.pat and acadiso.pat (acadlt.pat and acadltiso.pat for AutoCAD LT) files. You can add custom hatch pattern definitions to these files.
• Solid fill. Fill an area with a solid color.
• Gradient fill. Fill an enclosed area with a color gradient. A gradient fill can be displayed as
  a tint (a color mixed with white), a shade (a color mixed with black), or a smooth transition between two colors.

Gradients that mimic colors displayed on a cylinder, a sphere, or other shapes are
available.

Hatch Boundaries and Associativity

In the following illustration, the concrete hatches are bounded, while the earth hatches are unbounded.

By default, bounded hatches are associative, which means that the hatch object is associated with the hatch boundary objects:
changes to the boundary objects are automatically applied to the hatch.

Nonassociative hatches are not updated when their original boundary is changed.

Hatch associativity is turned on by default and is controlled by the HPASSOC system
variable. You can change hatch associativity using the Associate button on the Options
palette, the Properties palette, or the Hatch Edit dialog box.