{TAIL ~ The key lock} can be unlocked by {HEAD ~ a key} only when the combination lock is unlocked 
{ TAIL ~ The key lock } can be unlocked by { HEAD ~ a key } only when the combination lock is unlocked
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH