Square Knot, the first knot I learnt to tied when I was a Cub Scout. This basic yet useful knot is widely used in many situations, even in first-aid. 

Using Square Knot as a metaphor of NeuroSemantics and NLP trainings because these kinds of trainings is fundamental for a person to understand their behaviour, their emotions, their thinking and their values and beliefs, which making them THEM, this is also the reason why Dr. Bob Bodenhamer and Dr. Michael Hall name their NLP book "The User's Manual For The Brain".