{HEAD ~ A smoothly arched notch} extends axially to {TAIL ~ the topmost edge} of the box end 
extends axially to
{ HEAD ~ A smoothly arched notch } extends axially to { TAIL ~ the topmost edge } of the box end
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH