The straight curtain rod will need a shower or bathtub that is design in three-wall space only, even if it can be install in regular space, it will spend a lot of space that can be useful for other things, so it is not efficient. The materials that people usually use for their L shaped curtain rod is metal, however, you can also use iron or steel. It depends on the overall décor of the bathroom. Metal curtain rod that is finished with white color is good for more minimalist type of bathroom. Architecture.