This trick is called Trapeze Stall. It's one of the fundamental building blocks of fixed axle play. It looks like this. It's just a Trapeze, ordinary trapeze, but you'll notice the yo-yo is not spinning. It's about halfway wound up, or a little bit more. You can regenerate it, and do something else.
The way to do it is, you're going to throw Breakaway. Just Breakaway like that, coming back to your hand. And then while the yo-yo is out there in space, you're going to put your index finger out there and intercept it (the string) so that it lands just like that, a little bit wound up. To get out of it you just regenerate in the other direction.
So you're going to go over your index finger the other way. You can regenerate it to sleeper, or you can regenerate it across your body in a reverse Breakaway, or do something else. This is a really important trick for fixed axle yo-yoing. We do it in virtually any kind of combinations, or kickflips, or other kinds of variations. You can also do it from Forward Pass, if that's easier to learn.
Think about throwing Forward Pass back to your hand, and while the yo-yo's out there, just intercept the string with your finger, and you'll be like that. Which is exactly the same thing as the origin Trapeze Stall I showed. So as opposed to Undermount Stall where it's going in this direction, it's really the same idea, but you're going across your body in a Breakaway. Trapeze Stall. Have fun!