The boardslide, or railslide, depending on what you are sliding on, is an intermediate level trick, very popular and the basis for most other skateboard slide tricks. If you are comfortable doing a manual, ollie or 180, then you should try the boardslide.
Find a low rail, two sided curb or even a 4×4 piece of wood. Make sure that the object is sufficiently waxed. Ride parallel to the object, facing away (your back towards the object). Once alongside, ollie while turning 90 degrees, guiding your front truck over the object and resting the middle of your deck onto the object, make sure that neither truck is touching. You only need to ollie high enough to raise the front truck over the object. Your front foot should be on top of your front bolts, your back foot in the middle of the tail. While sliding, you can either pull out of the slide by popping the tail and turning 90 degrees back to your riding position or slide off the end of the object and turn 90 degrees.
The difference between a backside and frontside boardslide is in the direction you are facing while performing the slide. If you are facing forward, this is a frontside boardslide. Backside boardslides are considerably more difficult to balance.
If you are having trouble sliding, adjust your speed, you may be going too slow, or too fast to balance. Once you have mastered the boardslide try to do a shove it at the end of the rail.Boardslide Trick Tip - How to do a Boardslide on a Skateboard by Skatessentials