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