Heavy duty boxes contain thicker walls that would allow for stacking of heavy corrugated boxes without breaking during packaging and shipping. These come in single, double or triple wall boxes to ensure durability and stability. If a standard box is not strong enough to hold the items, use a single wall to add just a little extra box integrity during shipping. Single wall heavy-duty boxes are 40% stronger than the standard shipping box. Double wall cardboard boxes are a bit stronger than the standard box, and allow stacking and are great for moving. Triple wall boxes allow three times the protection of the standard corrugated boxes. All boxes are shipped and stored flat to save on space.