This tool works in conjunction with the 3D Designer Window and is used to mark out a specific area of the design to preview in this window. 

To use the tool, follow these steps;

1. Go to Window Menu > 3D Designer. The whole design will preview in the 3D Designer Window.
2. To zoom into a specific area, select the 3D Designer Tool from the Tools Palette and drag a box over an area of the design in the Design Window.
   
   The 3D Designer Window will update to preview only this section of the design.