for a rollercoaster, you use plywood to form the sideview of the rail. when you have 2 of these patterns with humps in them cut out, you use short 2x4's to attach the plywood by screwing threw the plywood and into the end of the 2x4. you do this around the perimeter and then you have your frame. then you can shape some plywood to the curves on top of the frame, screw them down, then take hdpe, lexan, or small diameter pvc that will adhere to the curve as your sliding surface. hopefully that makes sense.