The gap is chosen so that it is smaller than {TAIL ~ the thickness} of {HEAD ~ the loop regions} but larger than the thickness of the non loop region of the header tape 
The gap is chosen so that it is smaller than { TAIL ~ the thickness } of { HEAD ~ the loop regions } but larger than the thickness of the non loop region of the header tape
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH