I taught all my other dogs with bells. Best ones are the big sleighbells on a string. These are loud and you can hear them all over the house. You can get them in strips or strings in dollar stores. Right now some dollar stores are already stocking Christmas stuff!
You can wind around door handle and let hang down. Beware though ...LOL... once they catch on... they will ring the bell to fool you just because they want to go outside and play. You can be hopping up and down all day with a slick dog
