And a ROD is a long cylindrical piece of metal with a diameter somewhere between a WIRE (smaller) and a BAR (larger).
A ROD made out of wood is often called a DOWEL.
A BAR with a hole running through the middle of it is called a HOLLOW BAR. Since it is referenced by both its inside and outside diameters, it might be called a PUBE!!!???
Off-road racecar frames are often built out of PIPES. These frames have to carry large loads, and can potentially have very large impacts. So making them out of relatively thick wall, high quality, piping, such as is used in the Petro-Chemical industry, makes a lot of sense. Consider that such PIPES often carry highly toxic or explosive chemicals at extremely high pressures, yet still have to be reliably welded together at their many hundreds of butt joints. (Edit: the internal pressures can exceed the yield stress of mild-steel! Racecar frames are girly-boy stuff... )
As for the OPs original problem. I suggest you go to your local cafeteria and, ahem, "beg, borrow, or buy" one of their chairs or tables. Should be enough tubing there to finish your frame.
Z