A threaded fastener has {HEAD ~ a casing} enclosing at least three radially inwardly biased arcuate segments positioned to engage {TAIL ~ the threads} of a bolt or hollow threaded member 
A threaded fastener has { HEAD ~ a casing } enclosing at least three radially inwardly biased arcuate segments positioned to engage { TAIL ~ the threads } of a bolt or hollow threaded member
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH