This arrangement is used when the flyer is performing a trick that involves them passing forwards between the fly cables. The most common trick like this would be an Uprise (hence the name), but could also involve the flyer sitting up on the bar and jumping forwards (a Seat Jump). The lines are passed between the fly cables before starting, so they do not tangle during the trick.
ATTACHING: As you face forwards on the platform, hold the safety lines behind the fly bar and pass them towards you over the bar and between the fly cables. Then connect them to your belt as per Regular Lines. Make sure that, when you hold the bar, the lines not in between your arms.
TRICK EXAMPLES: Uprise, Seat Jump.
Note that not all Uprise or Sitting tricks require this type of lines. Tricks that don't involve the flyer passing completely between the cables (for example where they get up onto the bar and then get back off the same way (such as Back Hip Circle or Seat Roll), just require Regular Lines.
You can find out more about this trick in my books: