This is a group of tricks where the flyer is caught by their legs (or catches the other fly bar with their knees on a Bar-to-Bar rig) and then doesn't let go of their hands, so they remain suspended between the two trapezes.
The first variation is performed with a catcher. The flyer makes a Legs catch. At the moment of the catch, the flyer doesn't let go of their hands and thus remains stationary, suspended between the fly bar and the catcher. Once they want to continue, they either let go of the bar and swing down with the catcher, or the catcher lets go of their legs so they swing back on the fly bar.
The other variations are performed on a Bar-to-Bar rig. The flyer hooks their knees on the opposite fly bar at the frontend (either both knees or a single knee) and doesn't let go of their hands, remaining suspended between the bars.
You can find out more about this trick in my books:
Thanks to David for letting us know about this trick and providing a video.