So, in the picture, let me try to explain the routing of the line. It isn't readily apparent. First, the bitter end of the line that starts at the vang. If you start at the top of the picture, count down to the third line. Now follow it to the left. This ends at the lower block. This block is called a fiddle block with becket and cam. The line terminates (eyelet, bowline, some method of attaching to the becket pin) at the becket (sort of a pin at the upper right side of the lower left block in that picture). The line runs straight from the becket up and to the right. it travels under the smaller "pulley wheel" of the upper fiddle block. It travel over the top of that "pulley wheel" and back down to the lower left. At this point it is the line shown second from the top of the picture. It travels over the top of the smaller "pulley wheel" on the lower fiddle block, around and heads back up to the upper right fiddle block. Now it is the fourth line from the top of the picture. The line travels up and around the top of the larger "pulley wheel" on the upper fiddle block. From here it travels back down and to the left, now as the top line in the picture. Finally, it travels around the larger "pulley wheel" on the lower fiddle block, through the cam cleat, and back toward whatever sort of deck top line sorting device you have (not pictured) en-route to the cockpit.
I hope you were asking for sort of a step by step explanation and that this helped.
