Cardboard Box is used for boxing up other blocks to move them, preserving the inventory while being moved. By right clicking it on any block, tank, chest or machine, you wrap it in this protective box that you can break while still preserving everything about that block, tank, chest or machine. This includes its inventory, orientation, installed upgrades, and more, and should work with any block from any mod. You can later place it safely into the world. Sneak right-click to unwrap a box, causing the Cardboard Box to drop as an item.
Note that this functionality can essentially be used to move blocks as a substitute for Silk Touch. However, a blacklist appears in the configuration file that allows blocks to be blacklisted if desired. Also, boxes cannot be unwrapped in any inventory—only when placed in the world.