What about the clarinet leakage? If you know the clarinet leakage, first of all to confirm what caused the leakage, the clarinet before the knock, sometimes may be because the finger did not press the leakage, as long as the correct finger is no problem. If it is a leak caused by weak buttons, just adjust the tightness of the screws. Screws can not be too loose, do not be too tight, too loose sensitivity drops, too tight screws easy to collapse. If it is a bump caused by the air leakage will find a professional teacher to repair.