{HEAD ~ The cam plates} are in contact with the cam surfaces, and serve for positioning {TAIL ~ the sliding frames} 
{ HEAD ~ The cam plates } are in contact with the cam surfaces , and serve for positioning { TAIL ~ the sliding frames }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL