I did something like that last week with my T. I don't know if it is the same thing or not but that is what she called it. For me, she wanted me to imagine a clock and pick an hour that felt safe and ok for me. Then we went hour by hour to find out which ones didn't feel as safe. When certain ones felt unmanageable than I was allowed to go back to the time that felt safe and ok. I'm not sure how it worked but she called it Boundary Ruptures. I hope that helps.