QUOTE: "...I still don't get this -suppose the rod comprises of 1 handle and 1 piece and that handle can be detached from rod is that considered 1 piece rod or not?"
A one-piece rod is a rod that is one-piece, irrespective of whether the handle is detachable or not. Multi-piece rods are commonly called jointed rods. I don't know how to further explain this nor do I think it matters a whole lot. Use any straight cleaning rod with due care (avoiding contact by the rod with the crown of the muzzle during the stroke) and all will be ok. No need to complicate a fairly simple procedure any further.