Both knockdown and welded doorframes are made from steel. The main difference is how finished the frames arrive at your door.
Knockdown doorframes are not finished frames. They come in three parts, two doorjambs and one door header, which you put together yourself. This option is good for a professional who does not mind putting together frames and s working within a strict budget.
Welded doorframes come assembled and fused together and do not require additional construction. The frame’s joints that are welded together have been sanded and are smooth. Welded doorframes often are primed with paint.
Both knockdown and welded doorframes are often used in commercial buildings. They are similar and are often made from the same materials such as galvanized steel. Price the difference and evaluate whether you have the time and patience to put together the pieces of the knockdown frame. If you are running short on time and money, consider a ready-to-install welded frame.