I use a plastic rubbermaid container from walmart, I like it because is enclosed but leaves me full access by removing the top to help my bitch, also with the cover on is a nice cozy den feel for her and the puppies.
also I like the fact that I can wash it with bleach and water to keep germs at bay.
I breed silky terriers and find that this whelping box works best for me and my breed.
hugs,
CArmen in nj
Whelping box