At least a portion of the catch is positionable around {HEAD ~ at least a portion} of {TAIL ~ the tab} 
of
At least a portion of the catch is positionable around { HEAD ~ at least a portion } of { TAIL ~ the tab }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL