When the wheels move along the rail, {HEAD ~ the rake tines} travel along the openings in {TAIL ~ the screen}, forcing any obstructing material into another portion of the material reduction apparatus 
When the wheels move along the rail , { HEAD ~ the rake tines } travel along the openings in { TAIL ~ the screen } , forcing any obstructing material into another portion of the material reduction apparatus
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH