Sure it's a japanese way of doing things, and it requires A4 envelopes, but it makes sense.
The basic premise is that if you keep shifting things you read/access all the time to the left after you use them things will start shifting to the right. As such you get this lovely effect of those files that are super important, but never read, or files that you never read will move to the right where they can be picked up and sent into a more permanent storage.
Very wicked cool. And think of this, books that you refer all the time you could do the same thing. Every time you read a reference, take it and put it all the way to the left. Then those books you read all the time will become always the leftmost book (and it'll be easier for you to see that).