Rails

Are you slipping out and falling on your ass, or are you just sliding off the side early? For falling on your ass you should keep your feet about shoulder width apart with a bit more weight on your front foot. For sliding off the side of the rail you should make sure that you commit fully to 90degrees so that your completely sideways and also Look at the end of the rail, looking at the end is a big help.

i am just sliding off early

ill try that this weekend

what side are you falling off?

make sure you jump straight on. a lot of people fall off because they jump slightly to one side or the other. if you're falling forward, then its cuz ur jumping (to your left when facing the rail, forward when you're on it, either way you hopefully get what way im talking about) a little. try to jump as straight as you can, and if you still cant seem to get it, try to jump on and grab you're front foot inside edge (like you're going to front 2 off). that's what i do if i feel like im slipping off as well as adjusting my upper body. basically you're just gripping the rail, and it should make it so you land facing forward.