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