Open the loop with your left pointer finger, note the spinning tool is in place. Slip the bundle of fur between the loop legs to a point the match to a length close to half the hook shank length. When you have the fur in place, pinch the loop legs at the point they touch the fur. If you try and remove your left finger with out pinching the fur in place, the fur will drop out of the loop due to the vibration created by removing your finger. Once the finger is out of the loop the fur will be held in place. Pinching the fur after it's in the loop allows you to remove your left hand finger
This is when you will come to see why we closed the legs of the loop with the wrap around turns of thread. Had we not done this the loop would be open by the thickness of the hook shank and the material would drop out.