{HEAD ~ The chains} 17 are located at {TAIL ~ a position} lower than the level of the moving surfaces of the rollers 13 
are located at
{ HEAD ~ The chains } 17 are located at { TAIL ~ a position } lower than the level of the moving surfaces of the rollers 13
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH