Japanese 3" cd snap packs: what are they for?

[PoloPony]

So, ever since my big brother bought one for me in the early 90s I wondered what the heck are you supposed to do with these snap packs? Fold them? break off the plastic? the instructions were never clear and apart from the fact that I would never ever do it, I would really like to know what you were supposed to be able to do with them. Anyone? I tried to google them, but to no avail.