This is an amazing retrieve boosting game and continues to build value in boundaries too!
If you have a dog who willing goes out to get a thrown toy but then is reluctant to come back to you, this is the game for you.
Simply position yourself behind the boundary (which they already suction to) and throw a piece of food away and watch what the dog chooses to do. As they return to the bed (like we know they will), reinforce their decision to return. Then after a few throws with food, throw a toy and see where they choose to go? When they return to the boundary reinforce that behaviour and then return to throwing food again.
Gradually mix in the toy toss more often, being sure to still randomly ping-pong between food to keep their desire to retrieve high. Over time remove the boundary, then add in your cue word and voila: an amazing retrieve!