a slider held within the housing and in sliding contact with the second portion of {HEAD ~ the arm} inside of {TAIL ~ the housing} 
a slider held within the housing and in sliding contact with the second portion of { HEAD ~ the arm } inside of { TAIL ~ the housing }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL