When adding a Hatch, you will see an option called Associative on the Options panel of the Hatch Creation tab. If you keep this option checked, it will create an Associative Hatch, and keeping it unchecked will let you create non-associative Hatches:

Associative Hatches are ones that are "associated" or linked with the Hatch boundaries, and when you modify the boundary of the Hatch, the Hatch automatically changes to fill the modified boundary, whereas non-associative Hatches have their own boundary and changing the boundary of the drawing does not affect the Hatch.

In the screenshot that follows, a Hatch has been applied in the rectangle and, later, one of the lines of the rectangle was changed to an arc—the resulting Hatch automatically adjusted as it is an associative Hatch:

In the following screenshot, the same process has been repeated; the Hatch is applied to the rectangle and, later, one of the boundaries of the Hatch is converted to an arc, but it does not affect the non-associative Hatch:

When you make Hatches associative and then want to change them back to a non-associative type, select the Hatch pattern again and then uncheck the Associative option from the Hatch Editor tab. Non-associative Hatches can't be changed to associative Hatches.

The next option is all about making Hatches in open boundaries with tiny gaps. We will use a tool called Gap Tolerance for this, which is discussed next.