PVC is an ideal material for use in whelping boxes because it's strong, durable, easy to clean, and lightweight. If you're looking for an easy way to keep your whelping area clean, PVC is the way to go. PVC tubes are often used to create puppy rails, a.k.a pig rails for a DIY whelping box. They’re easy to assemble, easy to secure inside the box, easy to clean, and cheap to purchase.