When one of the shape operations is active, it is possible to drag out a copy of the shape, seeing the outline as the drag takes place. When the drag is released, the shape is burned into the selected image planes. The Escape key may be used to cancel an action during a drag.
Specifically, one depresses the left mouse button in the Main Image Window, drags the mouse while holding down the button, and releases when the shape has been dragged out to the desired size.