There are two materials in this pack, 1. Cardboard Outer, for the outer flat surface, and 2. Cardboard Inner, for the inner corrugated surface.

HOW TO USE:
1. Duplicate your subject 3d model, so that you have 2 overlapping copies of the same 3d mesh.
2. Assign 'Cardboard Inner' material to one of the models and 'Cardboard Outer' to the other.
3. If you are using Cycles, THIS IS IT, you are done. However, if you are using Eevee, follow this last step:
4. (EEVEE ONLY) Select the model with 'Cardboard Inner' material. Go into Edit mode by pressing TAB, select everything by pressing A, and then press ALT+S to 'scale along normal'. Now just move your cursor downwards a bit. This should make that model a tiny bit smaller than the other.
This will fix any visual artifacts in Eevee.