Replying to What to use on a rainbow?

So I have this sick rainbow-shaped piece of birch wood that would be perfect for a rail.  I plan on cutting a flat top on it so it will be like a 3-4 inch wide rainbow box.  I want to put 2 small metal pipes on either side to make it slide better.  Does anyone know a hard pipe (i.e. not aluminum because my edges would catch) that is around 1/2 - 1 inch in diameter?  And once I get the pipe, any ideas on how to bend it to form the shape of the rail?  It's not a steep rainbow, about 12 feet long and only goes up about 2-3 feet at the peak.