The Tiger's Mouth

Classical Tai Chi is based on Wu Style Taiji. It has a rather unique palm and in particular a unique thumb position. A student expressed puzzlement over this in comparison to what he experienced in Hung Gar Kung Fu. He states that students are told to keep the thumb close to the hand so it cannot be grabbed or broken. The thumb is open from the index finger in Wu Style and the space in between is called the Tiger's Mouth or Hu Kou 湖口.

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The very gentle grip is seen in the photo of Wu Jianquan. 

The open thumb is seen on his left hand and you can see him gently gripping the opponents right wrist with a small tiger's mouth. This gentle grip allows for the maintenance of extreme sensitivity or "ting" jin, wherein there is no muscle contraction that would interfere with sensitivity to opponents movement. I'm sure that students can now intuit the advantages of this...