Barbara, a lot of puppies like the squeeky noise, as well as the fur on the flat rats. I see them in the ring mostly with puppies. Once they are in open dogs you don't see them used much. Most use a little food bait if anything.
I keep both in my pocket. If I need to get the dogs attention I might use the squeaky flat rat once or twice, and use the food for a reward. I only have one dog that thinks it is alive and really pulls his ears and tail up when he sees it. For him, I keep it in my bra (

) and just slide it out a little when he is looking at me. But you gotta be careful, I've lost one once... whoops.