{TAIL ~ The machine} includes a rotatable drum having {HEAD ~ a spaced pair} of cylindrically contoured surfaces 
{ TAIL ~ The machine } includes a rotatable drum having { HEAD ~ a spaced pair } of cylindrically contoured surfaces
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH