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