Crate training older dogs is accomplished in the same way as with puppies. The idea behind crate training is to teach the dog to wait to potty, rather than using the restroom on the floor. Unlike puppies, however, older dogs may need more time to learn.
Since dogs prefer to not potty where they sleep, crates used for this purpose should be large enough for them to lay down without leaving extra room for them to relieve themselves. Crates for training can be purchased at most pet supply stores and online in a variety of sizes. The process of crate training involves placing the dog in the crate while the owner is away and immediately taking the dog to an acceptable potty spot when released from the crate. It often takes a number of weeks for the process to work, but over time the dog learns that the only acceptable place to relieve itself is outside.
Caution should be taken, however, to not treat the crate as a punishment. Doing so can confuse the dog and cause it to fear the crate, which makes it harder to train. Responsible pet owners should also ensure that the dog gets plenty of exercise while being trained as the crate does not offer it an opportunity to run and play.