Also known as aviation seats. It is characterized by three fulcrums, so that the waist, shoulder, hindquarters at the same time leaning on the back of the surface. The three supporting points in space does not constitute a straight line, and thus the production of such a high technical requirements of the sofa, the purchase is difficult to choose more. It is difficult to ensure the position of the support point when the process of the sofa is masked, so that the user can not feel uncomfortable with the back of the sofa. Buy high back sofa to pay attention to the back of the three support points of the composition is reasonable and proper, can be determined through the test seat. The high back sofa is evolved from the couch. To improve the rest performance, but also with the footstool, placed before the sofa, its height can be the same as the front of the sofa seat surface.