Geometry Tool
If I use the geomtery to add some material zones (not sure what they are called) to some clothing, will I be modifying the original clothing item? I would prefer to work on a copy.. at least until I know what I am doing?
I clicked on the geometry tool yesterday for the first time. I don't know why...but I expected a new window to open. But that didn't happen. I thought I saw a slight flicker on the screen, so I thought a panel had opened somewhere. But I couldn't find one. I gave up for the night. Next day I started up Daz Studio and went to pose my model and I had this red circle curser. I thought...where's that arrow thingy. I went to the tools menu and saw that Geometry tool was still selected. Thought it was a toggle. But it didn't toggle. It was then I realized that that circle curser was probably related to the geometry tool. Next I wondered how to turn it off and get the universal tool back. I figured there must be another tool in the list, since it wasn't a toggle. At least I was right about that.
Definitely don't know what I'm doing here.

Comments
Others here can probably answer your questions better than i can, but being able to create your own material zones is really useful, especially if you need to make part of something invisible. This is really good with body hair, to prevent it from poking through clothing. This tutorial might help you: http://www.daz3d.com/forums/discussion/42088/tutorial-adding-surfaces-in-ds-with-the-geometry-editor-tool
By default you are not editing original file. Changes are only saved to the project file. You can save as a new asset to use later that retains those new zones