Parts List Scale Plate 2 pieces (stainless steel) A tie rod (16.9IN)2 pieces (aluminum alloy) B tie rod (11.4IN) 2 pieces (aluminum alloy) C tie rod (8.0IN) 2 pieces (aluminum alloy) Washer 2 pieces (silica gel) M5 Screw 12 pieces (stainless steel) M5 Star Knob 12 pieces (bakelite) Durable and Reusable The stainless steel device is durable, and the surface is anodized to prevent discoloration in humid or high temperature environments. The wood device is not conducive to long-term, it will expand and contract with the change of humidity, making the data inaccurate. Easy to Install and Remove Securely locks into place using 4x knobs,if your stair treads are very long, you can use more knobs,easy to set up and use. Mark Stair Treads Make marks on the front of the 1X2 board where you use this stair tread fixture.