The only time I've trailered my horse (when I bought him), he was in a slant load with a divider. There was a trailer tie in the corner that I hooked him to. There was no ramp, and he jumped right in (and out of) the trailer, so I'm not worried about that.
Do I get a trailer tie and tie him to the driver's side corner just like it were a slant load? Or do I just use his lead rope with a safety knot for that? Or do I leave him untied in there?