Spinning on a spindle only to have to either spin a second (or third) spindle's worth before being able to ply and end up with your final yarn doesn't have to be your only choice! If you only have a small amount of fibre, or *gasp* only one spindle, there is another way! Plying on the fly is a way to both spin and ply in tandem on one spindle, and end up with plied yarn by the time you are done. Participants should leave the session with the ability to spin and ply on the same spindle, end-ing up with a fully plied yarn.