All Timberline Struts are made from kiln-dried 2" x 6" Select Structural Hem Fir or Douglas Fir, which can withstand considerable compression and tension. Every strut is beveled on its outer edge to ensure that the plywood panels lie flat on the struts. We do not use automatic feeds or gang drills. All struts are individually cut and drilled at correct angles. In addition to purchasing lumber that is graded and rated for strength, we personally inspect each piece for knots, or warping. You get only top quality struts that are accurately pre-cut, pre-drilled, and color-coded.