Reference number 2 in {TAIL ~ parentheses} indicates {HEAD ~ a second machine frame} which is inverted and is intended for grinding the top sides of boards  
Reference number 2 in { TAIL ~ parentheses } indicates { HEAD ~ a second machine frame } which is inverted and is intended for grinding the top sides of boards
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH