{TAIL ~ The print head unit} includes a first print head , {HEAD ~ a second print head} , a third print head , and a print head frame  
{ TAIL ~ The print head unit } includes a first print head , { HEAD ~ a second print head } , a third print head , and a print head frame
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH