When I used to teach at the college, I would often reach out to employers to make sure that my students were learning the skills that they were looking for in potential candidates. One of the topics that always came up was "being able to read welding symbols". With this information in hand, I developed a lecture that would teach students how to interpret welding symbols. The AWS has 2 documents that I highly recommend purchasing for your library. The first one is AWS A2.4 Standard, Brazing, and Nondestructive Examination. The next one is AWS A3.0 Standard Terms and Definitions.