Updated by Colin
Containers are a generic term for anything that is used to "contain" the items of a shipment when it is shipped. Typically this would be a rigid box or an envelope but may also be a "virtual" item to indicate that no container was used at all, or some other form of wrap was used. Containers are one type of Packaging Feature and this article covers the specifics of this type.
Give every container a descriptive name and SKU. If you will be scanning the containers at the packing stations they will need barcodes as well.
Specify the container dimensions as they would be measured by the carrier. These dimensions will be used when requesting shipping labels and the weight will be used to estimate the final package weight. Do not specify dimensions for containers with "Satisfies Overbox: No" (described below).
The following sections describe the attributes that are set in the Container's "Packaging" tab.
All containers have a "Satisfies Overbox" value of either "Yes" or "No". If "Yes" then the container must have dimensions specified and if "No" then dimensions must not be specified.
Products that have "Requires Overbox: Yes" may not be packed in a Container that has "Satisfies Overbox: No", but products that have "Requires Overbox: No" may be packed in Containers with either Satisfies Overbox value.
Orders that have "Overbox: Yes" cannot be shipped in Containers that have "Satisfies Overbox: No".
In short, by specifying these attributes you can ensure that specific items and/or orders will always be shipped in an outer container rather than their manufacturer's packaging.
Allow/Disallow for Merchants/Stores
By specifying these attributes you can prevent certain containers from being used by certain Merchants. If neither Allow or Disallow are specified then the Container is valid for all Merchants and Stores.
Specify only Allow or Disallow and not both. If Allow is specified then only the selected Merchants/Stores will be allowed to use the container. Similarly, if Disallow is specified then all Merchants/Stores except those selected will be allowed to use the container.
A container's eligibility may also be managed from the configuration under System > Configuration > General > Packing Solutions > Containers. The final set of containers eligible for Packing Solutions will be the intersection of the two sets described by the Container attributes and the system configuration.
Use for Bin Packing
If this is set to "No" then the container will be excluded from the Packing Solutions system. This would be appropriate for containers that are only to be used for special purposes, such as custom-fit boxes. These special purpose boxes may still be assigned to a Packing Solution using training or Preprocess Scripts.
If this is set to "Yes" then it will be included in the Packing Solution evaluation system unless it is excluded by another method such as Allow/Disallow for Merchants/Stores (described above).
The "Fallback Only" option allows a container to be allowed to be used for Packing Solutions but only as a last resort in case no other container with "Yes" can be used for packing. This is appropriate to use for particularly awkward packages such as long skinny packages that are necessary for long skinny items but you do not want them to be used for normal shaped items.