We use a very heavy plastic mesh we found on Amazon called Tenax poultry fence. This is really strong, not something that can easily be chewed thru. We anchor underneath with strong magnet hooks, (from Amazon) only to unpainted surfaces. They are so strong we struggle to get them off, I know our dogs can’t pull them off. We attach it at the sides to our metal fence with zip ties. We wrap it under our stairs but you could go the whole length. You can cutout to match your unit as needed where the frame dips down. Of course you do have to crawl under the slide to get it secured. It's 4 ft tall so it folds onto the ground. In some places we can tuck it under our outdoor mat. At the corners where it folds we sit something heavy on it, a cooler or a storage tote. It lays flat but we add weight at various spots so there is not a spot to slide underneath it. This lets our 2 schnauzers move around freely, they can go under the slide for shade, we put a bed under there, they like it and it gives us all more room. We don’t leave our dogs outside unattended for any length of time. This has worked for us for years.
