When an ice ax is used to make a T slot base in soft snow, it cannot be retrieved after the last climber gets down and has to be left behind.
We were taught and shown (and I have forgotten, hence the question) a nice technique to make a base in soft snow using two ice axes one with the pick pointing down and another with the shaft pointing down, and joined to each other with a sling tied in a sophisticated fashion. The base can be used for rappeling. Tugging at a thin rope/cord tied to the aforementioned sling releases both ice axes and allows to retrieve them from below.
I would be very grateful to see a video or read a short description if someone knows how to do this. The search terms are too generic to return relevant results.