{HEAD ~ The indicator} is swept over {TAIL ~ the brake block} to detect variations of the inside brake block surface from the specified radius 
is swept over
{ HEAD ~ The indicator } is swept over { TAIL ~ the brake block } to detect variations of the inside brake block surface from the specified radius
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH