Board material classification: distinguishing mill board and straw board clarifies uses in binding versus packing in trade. Mill board is a tough, heavy, high pressure milled paste or paperboard from coarse or recycled pulp, calendered and suited to bookbinding, covers and panelling. Straw board is a coarser, yellowish board made from straw pulp or incompletely cooked straw, commonly used for packing and box making. The principal distinction is mill board's greater density, finish and suitability for binding versus straw board's coarser pulp composition and packaging uses.