Way to draw a template for copying another region

[sammyo]

Not quite sure how to google for this. Say an odd shaped region needs to have the background overlayed, like removing a patch. Is there a way to draw the edge of the patch, but copy the edge to the background, then copy the background within that patch?  I guess I can start to see how a sequence of layers and masks would work but it seems like an option I'm just missing and would be really useful.

Thanks

[rich2005]

I was hoping someone would decipher this one   Can you give some more details, a simple sketch might help.

I thought it might be a 'droste' an image inside the same image but I do not know.