Robert...
Are you using Thermwood CN or the SB Link? They may be similar, but I can only explain as it would apply to the SB Link.
When a job is loaded, and before it is nested, Click [Add Sheets] then [Off Falls]
When the Off Falls dialog is open, scan an Off Fall label. That should enter it. You may have to click [Load Selected]
The selected Off Fall must be the same as one of the materials in the loaded job to be used.
Return to main and click Nest in [X] or [Y]. Parts will be nested on your scanned Off Fall(s) prior to full sheets of the same description.
If you are using TWD CN, hopefully one of those guys will chime in.
Gary Campbell ShopBot Tools Production Support ShopBot (eCabinets) Link Training & Support