{HEAD ~ A compressed boat} may be assembled from {TAIL ~ two substrate boats}, one of which moves away from the other during loading and unloading 
assembled from
{ HEAD ~ A compressed boat } may be assembled from { TAIL ~ two substrate boats } , one of which moves away from the other during loading and unloading
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH