Cheap ideas: The best thing is to purchase a small child's wading pool. It makes a wonderful whelping box and they are easy to keep clean. The type you blow up, pups can't get out, mom can get in, she can't squash the pups against a hard side. and mom and dad can keep it very clean. A heating pad on low setting works well because the material (vinyl plastic) isn't so heavy the heat can't get through. /Gary Gabriel
Add a Whelping Box to Your Indoor Doghouse Now this is some serious building!
Whelping Woodhaven Style If this is your first litter, check out these handy hits; photos included.
Whelping Box or Litter Box
How to build a dog whelping box (in hand written instructions!)