Shimano instructs to insert the sharp end of the "oil stopper" to bleed the brakes:
What is this for? I would expect that the oil should just flow from/to the funnel when pumped into the system with the syringe from the caliper bleeding screw. The other, wide end of the oil stopper, with the o-ring, is obviously needed to prevent oil flowing out when the funnel is being unscrewed from the brake lever; this is clear. But why does one need to insert the sharp end?