Having an object to display a single material is easy, but sometimes you might want to use multiple materials for the same object. For that purpose, you can use material indexes. Look at the top of your Material panel options, and you will see that each object has a list of indexes to work with. You will start with a single index, but you can add more with the + icon on the right and remove them using the - icon.
Unlike what many people think, when starting to use this feature, each index has a relation to an object and not a material. Note the following screenshot:
Figure 4.11: Material indexes
You can add ...
