We use this in our slider when the weather isn't too cold:

http://www.drsfostersmith.com/produc...cfm?pcatid=675

The only disadvantage is that our slider door is narrower than most and when we have heavier guests over, we have to take the dog door out so they can use the slider door. Kind of for them. Everyone in our family fits, even though we have to go out sideways. The joke is that it is our "diet door" I think with a typical size door, there wouldn't be the "diet door" issue.