Board-backed envelopes are sturdy mailing envelopes with a rigid cardboard backing to provide extra protection for the contents inside. These envelopes are commonly used for mailing important documents, photographs, certificates, artwork, or any other items that need to be kept flat and protected during transit. The board backing helps prevent bending, folding, or creasing of the contents, ensuring they arrive at their destination in good condition. Board-backed envelopes usually have a sealable flap for easy closure and come in various sizes to accommodate different types of documents.