Note that the block in the center of the bridle is in a fixed position: tied on. I like this Bridle arrangement for several reasons. Mainly, it allows you to bring the boom close to centerline of the boat without pulling the boom downward. This allows you to keep some twist in the sail if you want it and allows you to point higher than when the block can ride back and forth on the bridle. In the diagram the boom is away from centerline. With the conventional arrangement the leach would be hooked to weather. With this arrangement you can allow for some twist and improve power in a situation where it is needed.