Push the rapid bottler into your fermenter tap and then turn the tap on. Slip the bottle over the rapid bottler, so that the valve can be activated by the bottom of the bottle. Once this has been done, lift the bottle up so that it lifts the valve to allow the brew to flow into the bottle. Then fill the bottle to the top, and lower the bottle to shut the valve off. The displacement of the tube brings the liquid to the correct level to cap.