The angle of turn at each node is assumed to be 90° to the left. The picture shows the spirolateral.
We start at point O and move up 1 unit. Turn left and move 3 units, turn left again and move 3 units, turn left and move 4 units and turn left and move 5 units to end at point A. Repeat these steps after another left turn and we end at point B. Turn left and repeat the steps to take us to point C. Repeat, and we end back at point O, having drawn a symmetrical pattern.