Newborn puppies should be kept in a whelping box with their mother for the first several weeks of their lives. A pig rail, according to the Professor's House website, is a board or dowel inserted horizontally that should be installed to prevent the mother from accidentally smothering the pups.
A whelping box can be made out any sturdy, washable material. Finished plywood, pressboard or formica-like melamine work well. The box should fit the size of dog breed, with solid sides to protect the puppies from drafts. The bottom can be open for easy cleaning.
A pig rail should be installed on three sides of the box 3 to 5 inches off the bottom. It should extend 3 or 4 inches from the side of the box to give the puppies a safe place where they are protected from smothering by the mother. It can be made out of 2 by 4s, PVC or aluminum pipe, but any material will work.
Removing Pig Rails
The pig rails can be left on until the puppies are weaned, or they can be removed after three to five weeks, when the puppies are old enough to leave the box to relieve themselves.