The Tai Chi Cornerstones are the building blocks for advanced Tai Chi ch'uan practice. The basic form gives you the foundation, then the cornerstones give you the solid corners on which to build your "house". There are 4 cornerstones and all are based upon the Tai Chi Classics left to us by the Masters of old.
We have the "Crown being pulled up by string" which is the first and most important as it teaches us exactly where to place the weight. Then we have the legs, the waist and the hands. All 4 are then joined and co-ordinated so that your Tai Chi builds into your advanced practice.