A simply structured bi-functional roller skate has a pair of shoe embodiments. Each shoe embodiment is provided with a front securing seat which is a tubular device with a forwardly extended board, a rear securing seat which is a tubular device with a backwardly extended board. Both the front and rear...http://www.google.com.tw/patents/US20020125655?utm_source=gb-gplus-share專利 US20020125655 - BI-FUNCTIONAL ROLLER SKATE
