Hello people: I need some help, hope my bad english let me explain myself:

There was a hotkey or command I used, to do it but I can't remember it:

In the edge of a model I was able to select a vert, then, using this command create other vert over this, then moving one of this vert to a side and the new one to the other side, creating an inverted (putside down)  "V" shapped cut at the edge of the model. In the picture I show the vert where I want to do the cut.

Thanks in advance.