The present invention realizes spreading a sheet on a frame member by a simple structure and a simple process, and prevents uneven tension charged against the sheet. In the sheet spreading method of the invention, a core member for a backrest of a chair which is heated to around 200.degree. C. in a furnace...http://www.google.com/patents/US6292990?utm_source=gb-gplus-sharePatent US6292990 - Method of spreading a sheet on a frame member and method of manufacturing a chair by the sheet spreading method
