In the past, when screen printing was done, the paper used for carving cases was called wax carving paper. What is this? Where can I sell it?

That's not film, it should be called coated paper. It is to seal wax on sulfuric acid paper and then apply nitrolacquer. This method is too old and requires skillful carving and carving techniques. Now you just need to buy a post-it note with lettering on one meter. You can also carve patterns directly in the advertising company. Patterns should be mirrored and carved. Come back and stick it under the screen and flatten it. General water-soluble printing ink can be used.