Mod Assets

If you didn't know, your mod jar is basically a resourcepack!

Example:

Let's say the mod "Gold Sticks" wants to add replacement textures for multiple gold sticks. The gold stick is identified by goldsticks:golden_stick.
Now, the mod resources have the following file structure:

src/main/resources/assets/goldsticks/models/item/golden_stick.json
src/main/resources/assets/goldsticks/textures/item/golden_stick.png

src/main/resources/assets/goldsticks/citresewn/multiple_golden_sticks_2.properties
src/main/resources/assets/goldsticks/citresewn/multiple_golden_sticks_2.png

Now, multiple_golden_sticks_2.properties contains the following CIT:

type=item
items=goldsticks:golden_stick
stackSize=2-
texture=multiple_golden_sticks_2.png

If CIT Resewn is present(and Fabric API), it will load that cit from the mod jar. And if you have 2 or more golden sticks, the multiple_golden_sticks_2.png texture will be used instead of golden_stick.png!