Whenever its pointed tip passes the 12 o'clock position, the rotary hook hooks the higher thread. The bobbin case lies loosely inside the hook frame, allowing loops of thread to pass entirely over it with enough upper thread. The sewing machine's take-up arm then rewinds the thread that is no longer needed. If you've ever wondered what it's like to work with a rotary hook, or "complete rotary machine," you've come to the right place. Rotary hook sewing machines run more smoothly at faster speeds, are quieter, and have fewer thread jams than oscillating hook machines.