Starting from a hanging position, bring your feet up close to your hips.
Push out with your feet so that your hips move away from the wall.
At the same time, pull up with your hands.
Shift your grip so that you can push down with your palms.
Push upwards into a cast position; from there you can easily bring one foot on top of the wall, but one may have struggle putting a feet on the ledge, so he/she may use the shinbone to get upon the obstacle (although this should be avoided if possible).