I am considering using a training collar to teach my dog boundaries. I need to be able to keep her off leash, but she runs off if I let her off the leash. A fence, even an invisible fence, is out of the question as its not my house. I’ve tried teaching her boundaries for the last 5 months but it is not working well. She won’t respond to “come” unless she’s in the mood. I want to use a shock collar but I worry it may be inhumane. Are they effective and are they safe to use?