The riv-nut was originally called a plus-nut and was invented by BFGoodrich many years ago for the aerospace industry. Once their patent ran out other companies copied the design. Hence, there are many other names used for the same part today, such as riv-nut. It is a very good fastening system for blind applications. It consists of a threaded hollow barrel that is pulled it like a rivet, the blind end mushrooms out into 4 prongs like a cloverleaf. The hollow barrel is tapped for inserting a bolt. Take a look here...
http://www.perlanesales.com/plusnut_.php
and here...
http://cgi.ebay.com/ebaymotors/BRAND...RCHQ3aUSQ3a101