This invention provides a fastener which includes a shank having a head on one end and a conical portion on the other, the apex of the conical portion constituting a piercing point for the fastener. The shank includes a smooth cylindrical portion adjacent the conical portion and a threaded portion adjacent...http://www.google.es/patents/US3977142?utm_source=gb-gplus-sharePatente US3977142 - Floor nail
