The majority of support harnesses are meant to be be put on your dog while you need to lift him or take him outside, then removed again right away. That said, some full body harnesses can be kept on all day, so they're there when your dog needs help. More often that not, the latter kind of support harnesses are meant for pooches who only need a little additional help, but are quite mobile for much of the time, so you can't be sure exactly when they'll need support.