I am trying to secure the top of my staircase from my crawling baby. I want a gate with no threshold (i.e the whole thing swings freely) so no one will trip over it and fall down the stairs. I also want a gate that self-closes so I don't have to worry about my older children forgetting to close it.

I can't seem to find any commercial baby gate that has both of these features. If I buy a threshold-free gate, what can I add to make it self-close? Would it make a difference if it's wood or metal? We bought a spring self-closer gizmo that works for a light door, but I don't think it would work for a gate.