I've tried a number of filament clip designs, but they always get loose and floppy after repeated use. So I created this tiny clip which is meant to be used with the spring from a clothespin. I used some dollar store clothespins as spring donors; they are puny, too weak to use to actually hang wet clothing, but the springs are plenty strong enough for this purpose. Just clip the end of the filament against the side of the spool using the indentation provided and there you go.
The author marked this model as their own original creation.