How do your cats open doors?

I have observed my three cats and the neighbors cat opening our back door. The males (one of ours and one of the neighbors who prefers our food) push the door open with their face. The girls push against the door with their arms. In fact Reba the youngest often runs at the door full tilt and then jumps up and hits it with all four.

I am wondering if this difference is a male/female thing or if the division just happens to be amongst mine.

Weather permitting the back door is ajar during the day so they can come in when they are ready. I can tell the difference between my wife coming in and the cats. The cats don't shut the door.