I don't think it matters what you do, they will sometimes back door you, or come from somewhere you can't see them. I used to think it wasn't a big deal to place my call where I couldn't actually see it, as long as I could see all routes of ingress and egress. Twice, (and we almost never have snow), I had coyotes get all the way to the call and I never even saw them, just their tracks in the snow. Needless to say, I haven't done that intentionally in decades, but if you're hunting in broken terrain, you just have to do the best you can, and realize that sometimes they will make you feel dumb, no matter what you do.
