Abstract: An apparatus for drilling holes in multiple pieces of lumber of uniform width and which is capable of processing more than one width is disclosed. The drill bits are arranged in rows and the spacing between drill bits differs from row to row so as to permit the drilling of holes in more than one size of lumber. The header in which the drill bits are mounted is adapted to travel vertically along two parallel guides. Stabilizers prevent the lumber from buckling or shifting and help to ensure that the holes will be drilled in the same location in each piece of lumber. When a layer of lumber is conveyed to the apparatus, pistons lower the header which brings a spring-loaded horizontal stabilizer into contact with the lumber to stabilize the lumber. A second stabilizer pushes the lumber laterally to press the pieces of lumber together.