Pipe for bed?

That was just an example of how it works. I have the sides made at a sheet metal shop. They can make them as tight as you need. lot's of ways to do things. If your building sides anyway, braking them is clean, and saves a bunch of welding.

 

I used 1 1/4" x .125 tubing for the rails on my RPU when I fabricated the bed this summer.

 

Not bad at all!!

 

I used 2" exhaust tubeing on this

 

Take a piece of tubing. Whatever size you like.(1 1/4 to 1 1/2) Draw a line down the whole length nice and straight. Use a thin cutoff wheel cut a groove down the whole length. Slip it down over your sheetmetal side with a 45 or so degree angle on the top and weld it in a couple spots along the bottom side of the tubing. No need to weld the full length, Works good. I did it.