In their very simplest form, they were used for adding up. Ie green might be 3 and yellow might be 4. if you put both together, you would get 7, which might be a pink one. Can't remember what colours were what, but certainly remember the rods!! I think they were used for much more than that, but it was all too long ago now for me to remember!!!
I'm either older than some of you who don't remember them, and/or younger than others of you that don't remember!!!
