Dog beds

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I want to buy my dog a dog bed. He's a four years old Jack Russell terrier and has never had a dog bed before. He usually sleeps in our bed, but as our baby is getting older I want to give him some places that are only his so we can teach both our baby and our dog that the dog bed is a place where our dog is to be left alone. In your experience, what did your dog like best? Round or square bed? With edges or no edges?