The present invention is directed to a fastener device that includes a base portion. At least one shank is coupled to the base portion. The at least one shank includes an end configured to be driven into a material. The at least one shank also includes a weakened shank region disposed between a first...http://www.google.es/patents/US7104741?utm_source=gb-gplus-sharePatente US7104741 - Fastening means and process for its manufacture
