Oriented strand board

Oriented strand board, commonly called OSB, is a type of particle board which is made of carefully positioned strands of wood. Aspen and other similar woods are cut into long strands parallel to the . It is manufactured into sheets made up of wood strands, wax, and resin adhesives. Sheets are formed under pressure and heat. The finished sheet size varies by country. OSB is very strong making it ideal for building construction. Its most common uses in construction are for covering walls, floors and roofs before the finish products are applied. 
OSB can also be made from trees from areas burned over by forest fires.