{HEAD ~ The runner} is accommodated at {TAIL ~ the fixing portion}, and is capable of up and down sliding movements at the fixing portion 
{ HEAD ~ The runner } is accommodated at { TAIL ~ the fixing portion } , and is capable of up and down sliding movements at the fixing portion
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH