Knock on gallbladder meridian is a very popular exercise in Asia. It was first metioned from Wu Ching Zhong's (Alex Wu) book, "The Users' Manual for Human Body" (Chinese), he describes a simple way to boost your energy (Qi) and blood: 

It is simple, just 

1. knock on your gallbladder meridian once a day,

2. Maintain a good habit of sleep earlier.

3. Massage your pericardiium meridian everyday.

Hitting or knocking on gallbladder meridian is quite simple, it will take you not more than 15 minutes to do it. The other part of getting to bed early, however, is easier said than done. That is usually because people donˇt realize how important it is to do so. If they understand its importance, they will be able to adjust their life style gradually. 

Where to knock?

Actually, you only need to knock four GB points: GB26, GB30, GB31, GB34. Hit those points rigorously every day. Each time knock four times. Knock both sides of legs fifty times each day. This means two hound times total on each of right and left sides. Because leg muscles tend to be thick and contain fatty tissues, it requires extra effort to knock. Two knocks per second is a good rhythm to effectively stimulate acupressure points.

Goal:

This exercise is to stimulate Gallbladder meridian, forcing gallbladder to produce more juice (which is manufactured by liver); therefore, improve bodyˇs ability to absorb nutrition and make sufficient substances for our blood-making systems.

Extra Benefit:

Knocking on Gallbladder meridian can increase the intensity of our Gallbladder activities; thereby improve its removal of the wastes accumulated along the gallbladder meridian especially where buttocks hit outer legs. This exercise can directly reduce fatty tissue accumulation. Within one to two month of routine knocks as described, you will likely feel that you need a new pair of slimmer pants.