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At this point the specified geometry can be checked in order to make sure all has gone well; Click on View > Cross Section Solids, as shown below;
If you click on the 1 Cross Section, , in the Tree Outline and then click on the light blue dot, , you should now see a three dimensionally rendered beam in an isometric view;
At this point, the Design Modeler window can be closed. Don't worry - your work will be saved.