As I see it, for instance, search engine "Nail Knot". Instead of a nail or a straw, the vee holds the lines loose until one or both lines are drawn back through the middle or groove of the vee and cinched tight as both the lines are being removed from the end of the vee. Not to be flip, but the tier doesn't actually tie the knot; it just serves as a frame or jig or form for keeping the lines loose until the lines are woven together back through themselves and finally cinched tight with the long ends clipped neatly. It merely facilitates.
Answered on 12/20/2012 12:00:00 AM by ClothesHorse from Near Charlottesville, VA, USA