Tuck & Under
To train tuck, lure your dog with a treat under a chair or something he can easily get under. At first just let him put his head under and give him the treat. Then lure him a little further and keep at it until he is all the way under. Be careful that he has an easy escape if he starts to feel nervous. You don’t want him flipping over the chair or bumping his head, so take this very slow. Once he’s under and comfortable, reward him and tell him to stay or settle. Use settle more as a long term command.
With Zelda I gently touch her tail to bring it in. Eventually she will bring it in without my touching it.