A fiber glass board useful as a form board for lightweight cement and the like is strengthened by providing for the fibers to be predominantly oriented generally parallel to the major faces of the board in directions both parallel to and transversely of the dimension of the board corresponding to the process direction. A downstream conveyor which moves the blanket of fibers through the curing oven moves faster than the collection conveyor, thereby producing a drawing effect on the blanket and causing the desired fiber alignment. A glass fiber mat is applied to one or both major faces of the blanket prior to movement through the oven to provide additional stiffness to the board.