This is a really bad example, but say you agreed to purchase the home for 100,000. You can only put 10,000 down.
The appraisal comes in at 80,000. You then ask the seller to carry back/finance 10,000. So basically your bank will finance 80,000, you will put down 10,000, and the seller will hold a note for 10,000 (which you can maKe payments on) So that the seller still gets their asking price.
It's really not worth the hassle for 5,000 but it's an option.