A soft-sided pen rather than a wire cage, which changes what it is for — containing a puppy or a litter safely rather than confining a dog that wants out.
Mesh sides mean the animal can see you, which settles most of them far faster than a solid crate. It folds flat, so it travels and it stores.
For a whelping box, put it somewhere quiet and warm with the mesh facing away from foot traffic. For a puppy, it works best in the room you are actually in — the point of mesh is visibility. Wipe rather than machine wash the panels, and dry it fully before folding, since mesh left damp in a bag will mildew.
