Here are the types of machining regions you can choose from:

1.Part Regions  
Used in all 2½ axis operations, these are part curves that drive the location of the tool.  Defined from the Part Regions sub-tab of the Control Geometry tab for each operation.

2.Containment Regions
Used in most 3 axis operations, these are part curves used to contain the tool within selected areas.  Defined from the Containment Regions sub-tab of the Control Geometry tab for each operation.

3.Surface Regions  
Used in 3, 4 & 5 Axis operations, these are part surfaces that drive and/or contain the location of the tool.  Defined from the Part Regions and Part Surface sub-tab of the Control Geometry tab for each operation.

4.Avoid Regions
Used in 2½ machining operations to define 2D curve regions to be avoided by the cutter during machining.  Defined from the Avoid Regions sub-tab of the Control Geometry tab for each operation.

5.Start Points
Allows selection of points that can be used to determine the start / entry point for certain type of toolpath methods (Pocketing and Horizontal Roughing).  Defined from the Start Points sub-tab of the Control Geometry tab for each operation.

Select a Containment Region first before selecting an Avoid Region.  Regions can be selected using one of the following options:

1.Select regions using the Select button on the menu bar.

2.Select regions graphically in the display window.

3.Select regions when creating or editing an operation from the Control Geometry tab of the operation's dialog box shown below using:

Multiple regions can be selected by pressing the CTRL button. These selected regions can be used to create machining operations. The regions can be unselected using the None option (Select > None).

Once a machining operation is created, new regions can be selected or existing regions can be removed from the operation as well.

To edit the list of regions used in an existing operation, expand the folder corresponding to the machining operation in the Machining Browser window. Double-click on the Machining Regions icon. This will bring up the selected machining regions dialog. Now you can edit the list of regions using

•Remove All to remove all the selected regions.  

•Move Up/Move Down - these allow you to move a selected Drive Region Up or Down in the list

•Remove Active by selecting a region from the list of Selected Machining Region(s)

•Select regions using one of the Select buttons in the dialog.

The display of the regions in the part file can be toggled on/off using the Layer Manager.

Rhino allows you to save/export regions as curves in 3dm, Dxf, Dwg & other supported formats. Such a file can then be loaded into any part file to generate machining operations. To access the Export and the Import functions look under the File menu bar entry.