Hard panels formed from a wood-based material and having a decorative layer for floor coverings are provided, at least on two opposite edges, with coupling devices made in one piece with the panels wherein similar panels may be coupled together to form a floor covering, wherein these coupling devices...http://www.google.es/patents/US7343717?utm_source=gb-gplus-sharePatente US7343717 - Floor panel having tongue and groove coupling edges
Floor panel having tongue and groove coupling edges
