Horse stall question?

Well you could try tying a rope between the two, (if there isn't one already) and see if that helps keep the two apart. Then it would be much easier to get one or the other out. Or you could simply put cross ties in the stall and hook the one that you aren't taking out to it. Sometimes I have the same problem when I'm getting the horses out of their paddock, so I always make sure to bring a lead rope so I can shoo the others away, or you could use your hands or a crop.