Boxes come in very handy in witchcraft. You can use them to store your tools, and you can also use them in spells.
Box spells, such as the old standby money box are a staple in my practice.
Box magic usually revolves around the "feeding" of energy to a long-term thought-form such as prosperity, peace and the like.
In these sorts of spells the box thus represents a sort of magical "battery" that energizes that area of your life, and grows over time.
Here's an example of a money box spell: