Here is how I handled the "no nails" restriction: I bought lumber tall enough to go from ceiling to floor (2 pieces for each side of my small closet. I marked these boards with a line and nailed in quarter rounds with the flat side up. Next, I cut shorter boards that would just fit inside the space created by the long boards. When the long boards were stood up and the shorter boards were slid in and onto the quarteer rounds, there was/is no way these will fall down. When I move, all I have to do is pull the short boards out and take out the long boards. No nails.