Paper Bag Shag
When a piece of smoking hot gammon has a nice rack and rear, but not a face to match. The only way you would give her one, would be if you put a paper bag on her head so that you enjoy the benefits of her body, but you can imagine she is someone else. Hence; she is a Paper Bag Shag.
"That Sarah Jessica Parker, would ya?"
"Only if she had a paper bag on her head"
"too right, she is definitely a paper bag shag"