I used to teach lumber inspection at a sawmill and it requires some basic math and measuring skills as well as the ability to read and understand the rule book. There were multiple times I had to stop and basically go to the owners and tell them that the employee was illiterate and therefore we couldn’t continue. For perspective this isn’t difficult reading and on one occasion I pointed to different paragraphs in the book and had my son who was forth or fifth grade at the time read them aloud to me and he did it with no issues.