I needed another Rolodex-compatible file, but didn't want to pay for a real one. So I made one from a box-bottom and a pair of chopsticks.
Not only was it free, but it took all of five minutes to make (mostly because I took pictures), and it weighs less than the black plastic kind.
I used a box that was just a bit shorter than the chopsticks, but wider than the cards.
To line up the chopstick guides, I outlined a card on either end in pencil. Since each chopstick was going to thread through only two holes, it wasn't critical that the card on the front of the box and the card on the back of the box align exactly.
The important measurement is the distance between the holes.
A corkscrew's point was perfect for starting the holes. Don't make them too wide, because tighter holes will hold the chopstick more securely.
Push the narrow end of the chopstick through the outside back, and then the inside of the front.
I left mine as is, but if I were planning on heavy use, I'd attach a couple of wooden dowel caps to the four tips with glue-gun glue, to secure. (In the picture below, I'm demonstrating this with a couple I had on hand that had faces drawn on them. I didn't do this to mine.)