One thing that I've never liked in AutoCAD was its hard to make custom hatch patterns. There are some nice lisp codes out there that can do this for you but I've never seen one do circles. And most bloat the drawings up really quick. Well with the New Dynamic blocks in AutoCAD 2006 its possible to make a Dynamic block hatch pattern. All you need to do is create a block module say 4"x4" square. (You can make it any size you want. I just use this number because its pretty basic) Then simply add some dynamic properties and Vooala!! You can create custom patterns. If the hatch you need is not a simple rectangle or square you can use the XCLIP command and draw a polyline around the area you want to clip. You can also use the Express tool CLIPIT by selecting a closed polyline.
Steps to create your own>> Dynamic Hatch block
1) There is a block in the attached Drawing called RoundRocks. Its about a 4"x4" size. Create a block similar to the one in the drawing, with the geometry you want. The reason why I use a nested block is the Dynamic block, is the ARRAY action responds a lot faster when its arraying one entity, compared to all the little circles associated in it.
2) Now BEDIT the Rocks Dynamic Block and insert your block into the same spot as the RoundRocks block is. Make sure to delete the RoundRocks block after. Simply double click the Hatch ARRAY and specify the block hatch you made. Note: If you used a block size larger or smaller than 4"x4" you need to modify the ARRAY Column Offset and Row Offset to the sizes you used. And move the XY parameters to the Block intersections.
3)Close the Block Editor and your block is completed.