A bottom gate holds its frozen bait in the tunnel until the blades have sliced {HEAD ~ the bait} into {TAIL ~ pieces} 
into
A bottom gate holds its frozen bait in the tunnel until the blades have sliced { HEAD ~ the bait } into { TAIL ~ pieces }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL