|FAQ - Cart Help Buttons - Cart Settings - 8. Advanced Settings
This will force some/all products to prompt the customer to choose a shipping method from the Approved Shipping Methods. Some products may still require a product weight to calculate proper shipping charges.
If you choose to use this feature, it is important to have a shipping method in the Approved Methods list.
Note: You can use this feature to give your customers the choice of multiple options without having to recreate your products' "Add to Cart buttons". Also, this option will not affect products that are Shipping Exempt; you must remove the exemption first.