Use of {HEAD ~ three rails} makes a total length of {TAIL ~ the slide rail} shorter to provide a compact slide rail 
Use of { HEAD ~ three rails } makes a total length of { TAIL ~ the slide rail } shorter to provide a compact slide rail
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH