I may be mistaken, but I think this is another idea that Robert Heinlein invented(along with the water-bed)
I seem to remember the kid in the story mentioning the nipple clipped to his collar when he was on his 'Solo Survival' Graduation exam.
Heinlein was also BIG on caring a good knife with you.
The kids survival teacher, gave him his to carry, and told him to carry his own too, because he would never deprive someone of his personal knife.