This is how you can learn how to easily accomplish a parkour rail balance. When you first start out, use a rail that is close to the ground; you will probably fall several times while practicing. As you get more used to it you can use rails that are higher. Start out by walking across the rail slowly; keep your feet forward or curved, whichever you prefer. Eventually you will get faster and be able to jump from rail to rail. Just keep practicing and you will get the hang of it quickly.