These arent too bad. its pretty much jumping a rail but holding onto it still from the other side.

Place 1 hand on it with the palm facing down and the other hand with the palm facing up from underneath the bar

The reason its in a reverse position is so when you jump over its easier to hold on.
The hand with the palm facing down will actually let go of the rail and then grab hold again when your on the otherside.
When you have done that you should position yourself like a cat leap.
Theres your turn vault.

Dangers involved: None really its just clipping the rail that gets to the most of us.

If anybody can explain better then please do.

I also find it useful to focus on keeping my center of gravity over the obstacle. If you just launch yourself over the obstacle, you're likely to not be able to catch yourself on the other side and fall. If you look at the obstacle on your way over, and feel yourself rotating over it, you should be going ok. Also, keep yourself as close to the obstacle as possible, then you shouldn't over shoot.

But as with anything, practice makes perfect...

i've found a usefull idea is to lead your turn with your shoulder, push it over the rail first and this will carry yours body round with it.

i find it not better not to foucus on the move as much , and focus on the feet placement the otherside