About Associative Hatches (AutoCAD Mechanical Toolset)

By default, a hatch created with the AMASSOHATCH command is an associative hatch. When you change the contour of an associative hatch area, the hatch adjusts automatically to fill the new contour.

Note: You can also use AMASSOHATCH to create a non-associative hatch. In the Hatch contextual ribbon tab, under Options, turn off the Associative toggle button.
Note: Valid boundaries are contours and islands on contour layers. By default, the contour layers are AM_0, AM_1 and AM_2. You can define up to four contour layers in the Object Property Settings dialog box.