Cold War - Shoelaces Communication

One of the smartest ideas I have come across. Talk about hiding in plain sight! I mean ...sure...there are as many ways to come up with a coded language as there are people.... but when I read about how the CIA used different ways to tie a shoelace for communicating back in the 1950's.... I was quite impressed. There is even a book that was written on the various ideas that the CIA used at the time, it's called 'The Official CIA Manual Of Trickery And Deception', written by John Mulholland. Mulholland says, for a clever deception it "must be simple in it's basic idea". Which makes all the sense in the world because why would anyone suspect someone else who is really not doing anything out of the ordinary? Clever huh? Have you ever communicated in code? I used to have these secret languages in childhood...it sure was fun.