Did you know that during World War II knitting was used for codes. I saw a post in one of my groups and wanted to check it out more and found several articles. I think this is amazing.
Here are some of the articles I found:
QI: How knitting was used as code in in WWII
Knitting in code first article on the left
Historical Craftivism, Knitting and WWII
Those are just a few but they are interesting.