Tippy Table

Tippy Table  

This would be the table shape if was at a.

There are some circumstances where the table shape is too strong and too slow. This shape is a lighter, more flexible way to play. Black has the option of abandoning the stones if necessary when white tries (successfully) to cut through, usually getting a good result anyway. at b (the Trapezium Shape) is usually not good because a white play at a can then lead to the inefficiency of black having make an empty triangle with an additional play at c. at c is the bamboo joint.

reduction  

Diagram as from Keshi and Uchikomi: Black makes a nice reduction. is bad here, overconcentrated with respect to the wall, accordingly, should be at a, followed by at either b or c.