Crates are hard-shelled plastic cages with an opening at one end, usually closed by a wire or spoke door. Many dog owners endorse the use of crates for puppy training. Crates have been likened to natural dens that dogs make in the while. Since a dog will not usually foul his sleeping place, keeping a dog in a crate helps to teach him control. Dog owners who espouse crate training contend that the dog feels safe in the crate as he would in a den.

Crates are genuinely useful for transporting animals in a moving vehicle. Should an automotive accident occur, the hard body of the crate offers protection. However, no method of containment is recommended for any dog over a long period of hours. Pet owners who keep their dogs in a crate for eight hours a day may be protecting both the dog and their home from dangerous accidents but they are not providing the quality of life that a very social animal requires.

A good alternative to crate training consists of installing a doggie door adjacent to a blocked-off, puppy-proofed, "crate-sized" area in the house. As the puppy proves more reliable about going outside to relieve himself, his territory can be increased until he is trust worthy to have the run of the house.