Apply a Hatch to only Part of an Object

1) Draw a line or other polyline/polygon object so it intersects with the object to be hatched. This object is considered the control object. 

2) Select both the object to be hatched and the control object. 

3) Select Tool > Hatches, select the desired hatch, and click OK. 

4) Double-click on the portion of the object where the hatch should be placed. The hatch fills only the area between the click point and the intersection of the control line. 

As you can see in the example, the first object has an associative hatch that was applied through the Attribute Palette. The second and third objects use a non-associative hatch that was applied through the Hatches command. If the control line needs to be invisible, simply change the pen color to white.