Underlayment is produced using thin layers of wood called veneers that are peeled from a western softwood tree log and glued together to form one multi-layered wood panel. This process creates a very strong plywood underlayment that is engineered to be a durable protective covering and can be applied directly over the floor joist framing of a building. B-crossband plywood is a type of plywood that has a solid cross-band next to the face and a B-face that has been fully repaired.