baby gates

I'm not sure where to put this, so I figured this was an ok place. Addison is still rather new and a little afraid of coming out of my room unless I coax him out and he's sure its quiet and safe. I leave the door open so he doesn't feel trapped inside a tiny room all day, but he doesn't seem to want to come out.

My dog, however, likes going IN. I come home pretty much every day to see that she's eaten his food. He's not so afraid of her anymore, kind of ignores her, so I'm not really concerned about that. I just don't like that he doesn't have much to eat because she always eats his food! I've only caught her doing it once and she was very ashamed like she knew it was wrong, but she still does it when I'm not around.

I was thinking of getting some sort of baby gate but instead of putting it on the ground, having it about a foot or so up so he can come out, but she can't go in (she's a big dog). How secure are they? do they have to be on the ground or can I squeeze them between the doors well enough to hold?

Any other ideas on letting him come and go but keeping the dog out?