Two-footed take off (although a one-footed is better for flow, this is easier for a tutorial's sake). Comfortable distance away, and we all vary with this...ranging from about a foot up to almost 2 metres! Hands up and ready.

Often you're in the air before your hands on the rail, but since this is just a small kong, he's placed his hands on the rail first. This is also easier if you're attempting this for the first time.

Spring upwards with your feet, and push downwards slightly with your hands. Your spring will drive you forward and up, your push will make sure you have enough distance for your knees to clear. This is the stage when the angle you're leaning at determines distance (as do speed of run-up and distance of take-off). You want to lean forward more than you feel comfortable with (at least on your first go). If you're upright, your chest gets in the way of your knees, and you scrape. So just lean forward, and jump into the rail, using your hands to push yourself upwards.

As you can see, Dev is leaning further forward here. This means your knees aren't actually under your chest, but under your waist. This then means you don't have to rely on tucking far enough to get your knees over, because you release the rail by the time your knees get there.

Although this picture is similar to the above one, look at his hands. They're pushing downwards in a flicking motion. This drives the body upwards and outwards, ensuring that knees don't collide with the rail, and you get more distance.
When you need distance from a kong, exaggerate the leaning forward motion, and the push backwards from this flick of the wrist.

Knees and ankles over the rail, king kong complete (or monkey or whatever....if you were standing, it would virtually be the same).

And the safe cat-leap to the other side. It's actually quite a challenge to have such a small kong...your body leaning forward gives you momentum which drives you further.

This move is really something just to go for. All of Levity were doing it before Jump London was even dreamed of, because it's a very basic vault. Just go for it, and just remember to lean forward, and flick upwards slightly with your wrists. And bails don't hurt if that worries you - it's often just an ankle skimming the rail, and you land on your hands...it doesn't even cause bruising on concrete. And once you do have it, you'll find it replaces the old one-handed vault because it's just so much smoother and easier.