This is a group of tricks where the flyer grabs the catcher (or second fly bar on a Bar-to-Bar rig) and doesn't let go of their legs, so they end up suspected between the two trapezes.
Most common variation is performed with a catcher. The flyer does a Knee Hang catch. At the moment of the catch they tighten their knees so that they don't unhook from the bar. Both the flyer and catcher feel a small shock, but it is usually easy to hold on. They remain stationary, suspended between the two trapezes. Once they wish to continue, the flyer can either unhook their knees and continue to swing with the catcher, let go of the catcher and swing back on the bar, or let go of both and drop into the net. This trick is also possible (but harder) with a Single Knee Hang (or Gazelle).
The other variations of this trick are performed on a Bar to Bar rig. The flyer does a Knee Hang or a Single Knee Hang (Gazelle), catches the other fly bar and doesn't unhook their knees from the first, leaving them suspended between the two bars.
You can find out more about this trick in my books:
Thanks to Alon for providing a video for this page.