There are four main knots used to knot neckties. Knot theory is the study of mathematical knots. The constrictor knot is one of the most effective binding knots. In topology, knot theory is the study of mathematical knots. The knot sum of oriented knots is commutative and associative. The resulting knot is a sum of the original knots. Any knot can be uniquely expressed as a connected sum of prime knots. A knot invariant is a "quantity" that is the same for equivalent knots . Gusts of up to 16 knots were also observed. Trifoilers have clocked speeds upward of thirty knots. Airspeed is commonly given in knots (kn). A fast craft is a vessel capable of speeds over 30 knots. It begins with the elders making simple knots and braids for younger children. Most are endless knots, and many are varieties of basket weave knots. The circle is composed of four quarter circles, tied together with double knots.