In {HEAD ~ operation}, a user moves {TAIL ~ the belt sander} along the guide rails while the abrasive surface contacts the exterior surface of the work piece to smooth the exterior surface of the work piece 
In { HEAD ~ operation } , a user moves { TAIL ~ the belt sander } along the guide rails while the abrasive surface contacts the exterior surface of the work piece to smooth the exterior surface of the work piece
OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH