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How to create a polygon on a negative layer

I have Fab3000 Professional.  Is it possible to create a large (e.g. 2" x 2") polygon on a negative layer (e.g. ground plane)?  I'm having trouble understanding the ADD/POLYGON command.  It only seem to add an un-filled item.  Also, how about the reverse - removing a rectangle from an already filled polygon on a positive layer.

Great product so far and good value.
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Yes, it would be possible to create a polygon on a negative layer, and to create reverse rectangles, etc.  

(1) I would first recommend reviewing Composites. Understanding composites will allow you to create detailed polygon planes and metal areas with islands & voids. This is pretty much a unique feature with FAB 3000, so you may need to get used to the concept. Here's a forum link to get started:

(2) For example if you wanted to remove a rectangle from a filled polygon, you would simply need to add a clear rectangle inside that polygon.  To do this, perform the following.  
A. Select the filled polygon and find out what the composite level is for that polygon (usually it's 0).
B. Go to menu:  Add | Rectangle...
C. Change the "Composite Level" displayed in the toolbar (located upper/right), to "1".
D. Enter/click the two coordinates to create the rectangle.
Note: You will now see a clear rectangle in the middle of the filled polygon.  If you don't, then verify the following:  The composite level property for the clear rectangle must be one higher than the filled polygon; and make sure you are adding the clear rectangle to the same layer as the filled polygon.

(3) Essentially you can add/modify the appearance of any object, by changing the "Composite Level". Just select the object and goto the Properties dialog (menu:  Edit | Properties...) and change the Composite Level. 

(4) You  may also want to look at the feature called "Copper Balancing".  This feature allows you to quickly create complex metal areas using a defined clearance.  Goto FAB 3000 menu:  Tools | PCB Fabrication | Copper Balancing...

(5) There are several other useful composite layer features located in the menu: Tools | Composite Layers...

There are just a few suggestions and ideas, there are probably many other ways using FAB 3000 to create what you require.

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