A multi-layer and multi-chamber play structure developed with solid, rigid quadrilateral panels arranged vertically and including wall angle brackets therebetween located in the included angles of the panels. Double wall thickness platforms are arranged on platform angle brackets which span across vertically...http://www.google.com.tw/patents/US6099411?utm_source=gb-gplus-share專利 US6099411 - Multi-layer and multi-chamber play structure
