What are your views on keeping dogs in cages?

What are your views on keeping dogs in cages?
i have a puppy ,,,was wondering when u use the cage etc,,,im thinking just for night times with the door closed but have it as his bed area to have his own space and keep the door open all day...
also what age did u start toilet training,,and other training like the crying at night(what did u do etc)

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Dog Cage|Dog Cages