Thanks Holger! Jason and a friend built the whelping box. We have horse barn mats on the floor that are easy to clean, the dogs can not destroy them from digging and it also protects the pups from any chilling from the floor. Then indoor/outdoor carpet without the weaving so the pups will not get their nails caught. The third layer is foam eggshell or a thick blanket covered by a sheet. The bars are also removable. We did our best to make it bulldog proof...lol.