They are designed to tighten on a dog's neck (essentially a limited choke collar) so should not be used. Are you having problems with pulling on the lead?
I agree with Joy. Please don't use one. If you are having issues with pulling on the lead you could try a comfortable front attaching harness or the "about turn" method. Using LOTS of positive reinforcement at the beginning also convinces your dog that your side is the best place to be.
