Most crates are made of solid hard plastic or wire mesh; there are advantages to each. While soft-sided pet carriers work great for transport, they may be too small and prove too tempting for chew-aholic pups to work well for safe confinement. Solid plastic crates are generally opaque, so your dog won't be able to see much once it's inside. This can be either a plus or a minus, depending on your dog's need for privacy and the type of household it lives in. Plastic crates are a must if you plan to travel by air: airlines will not allow you to transport your dog in a metal crate. Wire crates offer plenty of air and visibility and are easy to clean. They can also be folded down and put away when not in use, which is a terrific feature for a smaller home.
There are a number of reasons to crate train your dog. Most puppies and adult dogs feel more secure in a small, enclosed den-like area, and young puppies are especially eager to find a safe place. A carefully-chosen crate and proper crate training can help your puppy discover that a crate is a safe, happy place to spend the night. A youngster should be introduced slowly to the crate when possible and not left unattended longer than the dog is able to "hold it" for potty training. But crate training, when it's done right, can give both you and your dog a feeling of order and security in a complex world.