Board backed envelopes, otherwise referred to as carboard envelopes, documents envelopes, do not bend envelopes, and certificate envelopes, are designed for posting items that need extra support during transit. They are commonly used for sending important paperwork, photographs, catalogues, certificates, contracts, marketing materials, and other flat products.

The brown board backed envelopes combine a strong paper front with a rigid board backing, providing extra support for flat content. The printed “Please Do Not Bend” message helps make handlers aware that the contents should remain flat.