It maybe simple but when I got these each lens came with a lens sack and a white string. Does anyone know what the white strings are for. I received three, one for each lens.

String is for tying a clove hitch around the existing leans to unscrew it.  Good old Boy Scout knot...

Thank you, funny thing is these are slip on and not screw on. They are for the standard. Maybe it

cont.. is for pulling off? I can only imaging the string goes around the lens in order to do this.