The foundation for crate training is based on the principle that puppies and dogs will avoid soiling in their immediate sleeping/living area. Crate training may also be used to retrain adult dogs as well. It is important that the crate is the right size. If it is too big the puppy or adult dog may soil in it. The crate should be big enough for your puppy or dog to stand up, turn around and lie down.
When unsupervised, puppies should be restricted to their crate. Never confine your puppy more than 2-3 hours as a time. The crate should be a positive experience not a negative one.