Slides need to be pretty level even front to rear as well. The little electric motors will be put under undo stress if tilted too much. I can't get completely level in my driveway without some added lift. I have put out my bedroom slide and could hear the motors working hard due to the tilt. They still did the job but I don't want them to wear out prematurely. So if I need to open up the inside I use boards under my jacks for extra lift and chock the front wheels...I'm lifting the rear off the ground just for better access while loading.