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