This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/fFL7f6Mc9V6 I hope you like it. I played around a bit with the length of the teeth. I had a problem where I would always need a comb, and never had one. Now that I carry a wallet around a lot more I figured I should design a comb with the same idea as a credit card knife. If you have your wallet, you have a comb! For this I would use the most rigid plastic you have. Also, I designed it with the exact dimensions of standard credit cards.