When your dog can sit, down, and stand on unique targets, you have a tool to use as you teach many of the advanced exercises. 

Sit: "M" and I demonstrate fronts and finishes, but you can also use this target to create very clear criteria on your sit stay.

Down: M and I demonstrate the down stay,  and the beginning of the Drop on Recall, but you can also use it on the Signal and Command Discrimination exercise. It is also a great aid to teach the very useful "go lie down," command. 

Stand: M and I demonstrate the stand stay, learning to maneuver her rear end, and beginning Signals. Don't forget it's usefulness when introducing the Go-out exercise.