The next step comprises folding {TAIL ~ each} of {HEAD ~ the first slotted partitions} along its folding axis 
The next step comprises folding { TAIL ~ each } of { HEAD ~ the first slotted partitions } along its folding axis
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH