@jeztastic There are a few different 'stopper knots', in essence its job is to prevent the rope to keep sliding by jamming a loop in it so even a random tangled section of rope that doesn't easily undo itself can work as a stopper knot. (Don't try that though)And in this case it's just to prevent the tail sliding in, causing the main knot to roll and undo itself.Whatever the knot used for the tail, no one should be clipping anything in that extra loop if it's there xD