Abstract: A breakaway pulley which opens and releases enclosed line when a knot in the line passes into the pulley. The pulley has two plates which are attached to each other by a hinge, with the hinge having a spring which urges the two plates apart. A pulley is on one plate, and a point of attachment is on the other pulley. The two plates are secured at the second end by a locking tooth which engages a notch, and which is released from engagement when the knot enters the pulley.