Make a selection with the "Rectangle Select Tool"
Select "Edit" > "Copy" Select "Edit" > "Paste As" > "New Layer"Now that it is pasted and a new layer, you have to tell the layer to be the same size as the image...
Right click on the layer you just created and select "Layer to Image Size" or...You can just right click on the layer you want to copy and select "Duplicate Layer" and edit that layer however you like.
signature.asc
Description: OpenPGP digital signature