The front 3 grids of the 2x3 "basement" level in my cage act as a door (it's propped partly open in this picture). It's kind of hard to see in the photo, but the corners on the left and right sides are cut so they can fit without connectors getting in the way. This kind of door would be easier to do with just zip ties and no connectors, but it still works very well this way. The only connectors on the actual door are the two on the bottom, and all three grids are zip tied directly to the cage on top. They swing up and down easily. I keep them closed with mini bungee cords attaching the door to the grids below the coroplast of the 2x3. To hold it open, I can clip it up to the grids on the front of the upper level.