This revolutionary, patented, shackle from Tylaska replaces the age-old knot! Unlike a conventional knot, the Tylaska Spool Shackle™ will not jam up and remains easy to fasten and unfasten even after loading up to the tensile strength of the line. The S-Series Tylaska P4 Spool Shackle™ is made of high-impact polycarbonate and has an exceptional strength-to-weight ratio. The key is that the line itself supplies the strength while the shackle simply redirects the force. The ease of unfastening after loading is equally amazing. Based upon the concept of “breaking the back” of a bowline knot, the line can be rolled back and taken off even after it becomes “stiff as a wire” from tension.