Puppy Pan is made with the strongest construction design we could make. This pan is made to withstand the use of a 20 lb dog. It will not buckle when filled with heavy litter.. puppy pads will fit into the bottom of the pan but will not lay flat because the bottom is curved and has rounded corners to make cleaning easier. Straight edge corners create a crevice that would be difficult to clean. Product Description Puppy Go Here Dog Litter Pan. Suitable for dogs that weigh 20 lbs or less. Puppies and dogs require training to use a dog litter box. Unlike cats, dogs do not automatically use a litter box. Please measure the space you have available for the litter box.. The photo showing the dimensions is for outside measurements of the pan. It is larger than most litter boxes. It should take 3 to 6 weeks or more to train a puppy or dog to use a litter box.