The bleeder can be pulled back into the slot with pliers, or pushed into a scrap of wood. In any event the back of the ferrule has a slot on both sides for the bleeder and a tighter fit.
If you use wood shafts, and mount your nocks, perpendicular to the grain in the wood (wood grain is then horizontal) when the arrow is nocked and your heads are vertical, the bleeder & slot is then in the same direction as the grain. It is then easier to clean the slot with the tool. Best to do this work on dull heads or be careful. I suggest using pliers to install or remove the bleeder.