I know that the drain can exit the side if the sink is located on the corner, from what little I've seen. But, there are models that have the sink in the middle with no cabinets beside the slide and when extended the slide is flush with the wall with nothing touching it. As I've been looking at floor plans I've also noticed that the base cabinets are only on half the slide possibly concealing the drain in the floor. Now if they are shallow slides, 12 to 16 inch, a larger base would cover the drain in the floor and not need a space cut in the floor of the slide so when it moves in it doesn't strike the drain in the floor. An example is the Apex 288BHS. I have a deep slide around 40 inches of floor space. I plan on 24 in base cabinets with an area built behind it for outside storage. The sink will be in the center of it. I can cut a space out of the floor so when it retracts it doesn't strike the drain but not sure on how to cover that opening in the floor. I thought of putting an acordoen style door in the floor so as it moves in and out it will be covered and not bind, but hey, I'm open to ideas.