IF crates are used,
1. they should be sized appropriately,
2. used with an “open door” policy (the dog can go in and out to suit its need/desire for a sense of its own space IF a given dog seems to need such a thing)
3. Only closed with dog inside for safety reasons when traveling.
Frankly, there are much better alternative to crates, no matter the situation. Proper training is the best alternative–of owners as well as dogs.
(If my barebones usage guide stated above seems to be in any way an endorsement of “crating” dogs, please be sure that it is not. I despise the things, in general, except in the case of those long-legged rats called Chihuahuas. . . Best kept there before being used in stewpots or as chum.)
Yeh, yeh, I’ve probably read all the excuses for “crating” dogs, and they’re all B.S. I don’t care to read ’em again. In almost all cases “crating” boils down to owners who are badly trained and unsuited to having a dog.